[Tests] add try/try_err helpers; convert tests to use them

Add `try` and `try_err` helper functions to `test/common.sh` that capture stdout/stderr and exit code from a single invocation, eliminating duplicate command executions in tests. Convert all existing tests that used the `OUTPUT`/`EXIT_CODE` double-invocation pattern to use the new helpers. Also fixes a pre-existing bug in the `nvm_die_on_prefix` test where ASCII apostrophes were used instead of U+2019 to match nvm.sh output.
2026-04-03 11:34:50 +08:00 · 2026-03-13 15:26:07 -04:00
parent 4c556a19b0
commit 14d01c6877
28 changed files with 329 additions and 365 deletions
--- a/test/common.sh
+++ b/test/common.sh
@@ -1,3 +1,29 @@
+# Runs a command once and captures stdout and exit code.
+# Suppresses xtrace in the subshell. Discards stderr.
+#
+# Sets: CAPTURED_STDOUT, CAPTURED_EXIT_CODE
+#
+# Usage:
+#   try nvm_version current
+#   [ "$CAPTURED_STDOUT" = "v20.0.0" ] || die "wrong output"
+#   [ "$CAPTURED_EXIT_CODE" = 0 ] || die "wrong exit code"
+try() {
+  CAPTURED_STDOUT="$(set +x; "$@" 2>/dev/null)" && CAPTURED_EXIT_CODE=0 || CAPTURED_EXIT_CODE=$?
+}
+
+# Runs a command once and captures stderr and exit code.
+# Suppresses xtrace in the subshell. Discards stdout.
+#
+# Sets: CAPTURED_STDERR, CAPTURED_EXIT_CODE
+#
+# Usage:
+#   try_err nvm_alias
+#   [ "$CAPTURED_STDERR" = "An alias is required." ] || die "wrong error"
+#   [ "$CAPTURED_EXIT_CODE" = 1 ] || die "wrong exit code"
+try_err() {
+  CAPTURED_STDERR="$(set +x; "$@" 2>&1 >/dev/null)" && CAPTURED_EXIT_CODE=0 || CAPTURED_EXIT_CODE=$?
+}
+
 assert_ok() {
  local FUNCTION=$1
  shift
--- a/test/fast/Aliases/'nvm
+++ b/test/fast/Aliases/'nvm
@@ -3,25 +3,21 @@
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 die () { echo "$@" ; exit 1; }

-OUTPUT="$(nvm alias foo#bar baz 2>&1)"
+try_err nvm alias foo#bar baz
 EXPECTED_OUTPUT="Aliases with a comment delimiter (#) are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias with a hash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias with a hash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to create an alias with a hash should fail with code 1, got '$CAPTURED_EXIT_CODE'"

-EXIT_CODE="$(nvm alias foo#bar baz >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to create an alias with a hash should fail with code 1, got '$EXIT_CODE'"
-
-OUTPUT="$(nvm alias foo# baz 2>&1)"
+try_err nvm alias foo# baz
 EXPECTED_OUTPUT="Aliases with a comment delimiter (#) are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias ending with a hash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias ending with a hash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to create an alias ending with a hash should fail with code 1, got '$CAPTURED_EXIT_CODE'"

-EXIT_CODE="$(nvm alias foo# baz >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to create an alias ending with a hash should fail with code 1, got '$EXIT_CODE'"
-
-OUTPUT="$(nvm alias \#bar baz 2>&1)"
+try_err nvm alias \#bar baz
 EXPECTED_OUTPUT="Aliases with a comment delimiter (#) are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias starting with a hash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
-
-EXIT_CODE="$(nvm alias \#bar baz >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to create an alias starting with a hash should fail with code 1, got '$EXIT_CODE'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias starting with a hash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to create an alias starting with a hash should fail with code 1, got '$CAPTURED_EXIT_CODE'"
--- a/test/fast/Aliases/'nvm
+++ b/test/fast/Aliases/'nvm
@@ -3,25 +3,21 @@
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 die () { echo "$@" ; exit 1; }

-OUTPUT="$(nvm alias foo/bar baz 2>&1)"
+try_err nvm alias foo/bar baz
 EXPECTED_OUTPUT="Aliases in subdirectories are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias with a slash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias with a slash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to create an alias with a slash should fail with code 1, got '$CAPTURED_EXIT_CODE'"

-EXIT_CODE="$(nvm alias foo/bar baz >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to create an alias with a slash should fail with code 1, got '$EXIT_CODE'"
-
-OUTPUT="$(nvm alias foo/ baz 2>&1)"
+try_err nvm alias foo/ baz
 EXPECTED_OUTPUT="Aliases in subdirectories are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias ending with a slash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias ending with a slash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to create an alias ending with a slash should fail with code 1, got '$CAPTURED_EXIT_CODE'"

-EXIT_CODE="$(nvm alias foo/ baz >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to create an alias ending with a slash should fail with code 1, got '$EXIT_CODE'"
-
-OUTPUT="$(nvm alias /bar baz 2>&1)"
+try_err nvm alias /bar baz
 EXPECTED_OUTPUT="Aliases in subdirectories are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias starting with a slash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
-
-EXIT_CODE="$(nvm alias /bar baz >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to create an alias starting with a slash should fail with code 1, got '$EXIT_CODE'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to create an alias starting with a slash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to create an alias starting with a slash should fail with code 1, got '$CAPTURED_EXIT_CODE'"
--- a/test/fast/Aliases/'nvm
+++ b/test/fast/Aliases/'nvm
@@ -3,25 +3,21 @@
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 die () { echo "$@" ; exit 1; }

-OUTPUT="$(nvm unalias foo/bar 2>&1)"
+try_err nvm unalias foo/bar
 EXPECTED_OUTPUT="Aliases in subdirectories are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to remove an alias with a slash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to remove an alias with a slash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to remove an alias with a slash should fail with code 1, got '$CAPTURED_EXIT_CODE'"

-EXIT_CODE="$(nvm unalias foo/bar >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to remove an alias with a slash should fail with code 1, got '$EXIT_CODE'"
-
-OUTPUT="$(nvm unalias foo/ 2>&1)"
+try_err nvm unalias foo/
 EXPECTED_OUTPUT="Aliases in subdirectories are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to remove an alias ending with a slash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to remove an alias ending with a slash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to remove an alias ending with a slash should fail with code 1, got '$CAPTURED_EXIT_CODE'"

-EXIT_CODE="$(nvm unalias foo/ >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to remove an alias ending with a slash should fail with code 1, got '$EXIT_CODE'"
-
-OUTPUT="$(nvm unalias /bar 2>&1)"
+try_err nvm unalias /bar
 EXPECTED_OUTPUT="Aliases in subdirectories are not supported."
-[ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "trying to remove an alias starting with a slash should fail with '$EXPECTED_OUTPUT', got '$OUTPUT'"
-
-EXIT_CODE="$(nvm unalias /bar >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = "1" ] || die "trying to remove an alias starting with a slash should fail with code 1, got '$EXIT_CODE'"
+[ "$CAPTURED_STDERR" = "$EXPECTED_OUTPUT" ] || die "trying to remove an alias starting with a slash should fail with '$EXPECTED_OUTPUT', got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" = "1" ] || die "trying to remove an alias starting with a slash should fail with code 1, got '$CAPTURED_EXIT_CODE'"
--- a/test/fast/Running
+++ b/test/fast/Running
@@ -11,30 +11,20 @@ cleanup() {
 : nvm.sh
 \. ../../nvm.sh

+\. ../common.sh
+
 nvm_make_alias foo foo

-set +ex # needed for stderr
-OUTPUT="$(nvm use foo 2>&1)"
-set -ex
+try_err nvm use foo
 EXPECTED_OUTPUT='The alias "foo" leads to an infinite loop. Aborting.'
-[ "_${OUTPUT}" = "_${EXPECTED_OUTPUT}" ] \
-  || die "'nvm use foo' did not output >${EXPECTED_OUTPUT}<; got >${OUTPUT}<"
+[ "_${CAPTURED_STDERR}" = "_${EXPECTED_OUTPUT}" ] \
+  || die "'nvm use foo' did not output >${EXPECTED_OUTPUT}<; got >${CAPTURED_STDERR}<"
+[ "_$CAPTURED_EXIT_CODE" = "_8" ] || die "Expected exit code 8; got ${CAPTURED_EXIT_CODE}"

-set +ex # needed for stderr
-EXIT_CODE="$(nvm use foo 2>/dev/null ; echo $?)"
-set -ex
-[ "_$EXIT_CODE" = "_8" ] || die "Expected exit code 8; got ${EXIT_CODE}"
-
-set +ex # needed for stderr
-OUTPUT="$(nvm use --silent foo 2>&1)"
-set -ex
+try_err nvm use --silent foo
 EXPECTED_OUTPUT=''
-[ "_${OUTPUT}" = "_${EXPECTED_OUTPUT}" ] \
-  || die "'nvm use --silent foo' did not output >${EXPECTED_OUTPUT}<; got >${OUTPUT}<"
-
-set +ex # needed for stderr
-EXIT_CODE="$(nvm use --silent foo 2>/dev/null ; echo $?)"
-set -ex
-[ $EXIT_CODE -eq 8 ] || die "Expected exit code 8 from 'nvm use --silent foo'; got ${EXIT_CODE}"
+[ "_${CAPTURED_STDERR}" = "_${EXPECTED_OUTPUT}" ] \
+  || die "'nvm use --silent foo' did not output >${EXPECTED_OUTPUT}<; got >${CAPTURED_STDERR}<"
+[ $CAPTURED_EXIT_CODE -eq 8 ] || die "Expected exit code 8 from 'nvm use --silent foo'; got ${CAPTURED_EXIT_CODE}"

 cleanup
--- a/tests/nvm_alias
+++ b/tests/nvm_alias
@@ -9,21 +9,19 @@ cleanup () {
 : nvm.sh
 \. ../../../nvm.sh

-OUTPUT="$(nvm_alias 2>&1)"
-EXPECTED_OUTPUT='An alias is required.'
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_alias' produced wrong output; got $OUTPUT"
+\. ../../common.sh

-EXIT_CODE="$(nvm_alias >/dev/null 2>&1 ; echo $?)"
-[ "_$EXIT_CODE" = "_1" ] || die "'nvm_alias' exited with $EXIT_CODE, expected 1"
+try_err nvm_alias
+EXPECTED_OUTPUT='An alias is required.'
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_alias' produced wrong output; got $CAPTURED_STDERR"
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] || die "'nvm_alias' exited with $CAPTURED_EXIT_CODE, expected 1"

 rm -rf ../../../alias/nonexistent

-OUTPUT="$(nvm_alias nonexistent 2>&1)"
+try_err nvm_alias nonexistent
 EXPECTED_OUTPUT='Alias does not exist.'
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_alias nonexistent' produced wrong output; got $OUTPUT"
-
-EXIT_CODE="$(nvm_alias nonexistent >/dev/null 2>&1 ; echo $?)"
-[ "_$EXIT_CODE" = "_2" ] || die "'nvm_alias nonexistent' exited with $EXIT_CODE, expected 2"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_alias nonexistent' produced wrong output; got $CAPTURED_STDERR"
+[ "_$CAPTURED_EXIT_CODE" = "_2" ] || die "'nvm_alias nonexistent' exited with $CAPTURED_EXIT_CODE, expected 2"

 EXPECTED_OUTPUT="0.10"
 nvm alias test "$EXPECTED_OUTPUT" || die "'nvm alias test $EXPECTED_OUTPUT' failed"
--- a/tests/nvm_compare_checksum
+++ b/tests/nvm_compare_checksum
@@ -8,66 +8,50 @@ die () { echo "$@" ; cleanup ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 set -ex

 nvm_compute_checksum() {
  echo
 }

-set +x
-OUTPUT="$(nvm_compare_checksum 2>&1 >/dev/null || echo)"
-EXIT_CODE="$(nvm_compare_checksum >/dev/null 2>&1 || echo $?)"
-set -x
+try_err nvm_compare_checksum
 EXPECTED_OUTPUT='Provided file to checksum is empty.'
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 4 ] || die "expected to exit with code 4, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 4 ] || die "expected to exit with code 4, got ${CAPTURED_EXIT_CODE}"

-set +x
-OUTPUT="$(nvm_compare_checksum foo 2>&1 >/dev/null || echo)"
-EXIT_CODE="$(nvm_compare_checksum foo >/dev/null 2>&1 || echo $?)"
-set -x
+try_err nvm_compare_checksum foo
 EXPECTED_OUTPUT='Provided file to checksum does not exist.'
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 3 ] || die "expected to exit with code 3, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 3 ] || die "expected to exit with code 3, got ${CAPTURED_EXIT_CODE}"

-set +x
-OUTPUT="$(nvm_compare_checksum ../../../nvm.sh 2>&1 >/dev/null || echo)"
-EXIT_CODE="$(nvm_compare_checksum ../../../nvm.sh >/dev/null 2>&1 || echo $?)"
-set -x
+try_err nvm_compare_checksum ../../../nvm.sh
 EXPECTED_OUTPUT='Provided checksum to compare to is empty.'
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 2 ] || die "expected to exit with code 2, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 2 ] || die "expected to exit with code 2, got ${CAPTURED_EXIT_CODE}"

-set +x
-OUTPUT="$(nvm_compare_checksum ../../../nvm.sh checksum 2>&1 >/dev/null)"
-EXIT_CODE="$(nvm_compare_checksum ../../../nvm.sh checksum >/dev/null 2>&1 ; echo $?)"
-set -x
+try_err nvm_compare_checksum ../../../nvm.sh checksum
 EXPECTED_OUTPUT="Computed checksum of '../../../nvm.sh' is empty.
 WARNING: Continuing *without checksum verification*"
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 0 ] || die "expected to exit with code 0, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 0 ] || die "expected to exit with code 0, got ${CAPTURED_EXIT_CODE}"

 nvm_compute_checksum() {
  echo "not checksum: ${1}"
 }

-set +x
-OUTPUT="$(nvm_compare_checksum ../../../nvm.sh checksum 2>&1 >/dev/null || echo)"
-EXIT_CODE="$(nvm_compare_checksum ../../../nvm.sh checksum >/dev/null 2>&1 || echo $?)"
-set -x
+try_err nvm_compare_checksum ../../../nvm.sh checksum
 EXPECTED_OUTPUT="Checksums do not match: 'not checksum: ../../../nvm.sh' found, 'checksum' expected."
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 1 ] || die "expected to exit with code 1, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 1 ] || die "expected to exit with code 1, got ${CAPTURED_EXIT_CODE}"

 nvm_compute_checksum() {
  echo checksum
 }
-set +x
-OUTPUT="$(nvm_compare_checksum ../../../nvm.sh checksum 2>&1 >/dev/null)"
-EXIT_CODE="$(nvm_compare_checksum ../../../nvm.sh checksum >/dev/null 2>&1; echo $?)"
-set -x
+try_err nvm_compare_checksum ../../../nvm.sh checksum
 EXPECTED_OUTPUT='Checksums matched!'
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 0 ] || die "expected to exit with code 0, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 0 ] || die "expected to exit with code 0, got ${CAPTURED_EXIT_CODE}"

 cleanup
--- a/tests/nvm_compute_checksum
+++ b/tests/nvm_compute_checksum
@@ -7,18 +7,14 @@ die () { echo "$@" ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh

-set +x
-OUTPUT="$(nvm_compute_checksum 2>&1 >/dev/null || echo)"
-EXIT_CODE="$(nvm_compute_checksum >/dev/null 2>&1 || echo $?)"
-set -x
-EXPECTED_OUTPUT='Provided file to checksum is empty.'
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 2 ] || die "expected to exit with code 2, got ${EXIT_CODE}"
+\. ../../common.sh

-set +x
-OUTPUT="$(nvm_compute_checksum foo 2>&1 >/dev/null || echo)"
-EXIT_CODE="$(nvm_compute_checksum foo >/dev/null 2>&1 || echo $?)"
-set -x
+try_err nvm_compute_checksum
+EXPECTED_OUTPUT='Provided file to checksum is empty.'
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 2 ] || die "expected to exit with code 2, got ${CAPTURED_EXIT_CODE}"
+
+try_err nvm_compute_checksum foo
 EXPECTED_OUTPUT='Provided file to checksum does not exist.'
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 1 ] || die "expected to exit with code 1, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 1 ] || die "expected to exit with code 1, got ${CAPTURED_EXIT_CODE}"
--- a/tests/nvm_die_on_prefix
+++ b/tests/nvm_die_on_prefix
@@ -6,6 +6,8 @@ TEST_DIR="$TEST_PWD/nvm_die_on_prefix_tmp"
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 TEST_VERSION_DIR="${TEST_DIR}/version"

 cleanup () {
@@ -23,23 +25,20 @@ die () {

 [ ! -e "$TEST_DIR" ] && mkdir "$TEST_DIR"

-OUTPUT="$(nvm_die_on_prefix 2>&1)"
+try_err nvm_die_on_prefix
 EXPECTED_OUTPUT="First argument \"delete the prefix\" must be zero or one"
-EXIT_CODE="$(nvm_die_on_prefix >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix' did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_1" ] || die "'nvm_die_on_prefix' did not exit with 1; got "$EXIT_CODE""
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix' did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] || die "'nvm_die_on_prefix' did not exit with 1; got "$CAPTURED_EXIT_CODE""

-OUTPUT="$(nvm_die_on_prefix 2 2>&1)"
+try_err nvm_die_on_prefix 2
 EXPECTED_OUTPUT="First argument \"delete the prefix\" must be zero or one"
-EXIT_CODE="$(nvm_die_on_prefix 2 >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 2' did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_1" ] || die "'nvm_die_on_prefix' did not exit with 1; got "$EXIT_CODE""
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 2' did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] || die "'nvm_die_on_prefix' did not exit with 1; got "$CAPTURED_EXIT_CODE""

-OUTPUT="$(nvm_die_on_prefix 0 2>&1)"
+try_err nvm_die_on_prefix 0
 EXPECTED_OUTPUT='Second argument "nvm command", and third argument "nvm version dir", must both be nonempty'
-EXIT_CODE="$(nvm_die_on_prefix 0 >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0' did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_2" ] || die "'nvm_die_on_prefix 0' did not exit with 2; got '$EXIT_CODE'"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0' did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_2" ] || die "'nvm_die_on_prefix 0' did not exit with 2; got '$CAPTURED_EXIT_CODE'"

 nvm_has() { return 1; } # ie, npm is not installed
 OUTPUT="$(nvm_die_on_prefix 0 version_dir foo 2>&1)"
@@ -70,26 +69,26 @@ node() {
 OUTPUT="$(nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" 2>&1)"
 [ -z "$OUTPUT" ] || die "'nvm_die_on_prefix' was not a noop when directory is equivalent; got '$OUTPUT'"

-OUTPUT="$(PREFIX=bar nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" 2>&1)"
+PREFIX=bar try_err nvm_die_on_prefix 0 foo "$(nvm_version_dir new)"
+unset PREFIX
 EXPECTED_OUTPUT='nvm is not compatible with the "PREFIX" environment variable: currently set to "bar"
 Run `unset PREFIX` to unset it.'
-EXIT_CODE="$(export PREFIX=bar ; nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'PREFIX=bar nvm_die_on_prefix 0 foo' did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_3" ] || die "'PREFIX=bar nvm_die_on_prefix 0 foo' did not exit with 3; got '$EXIT_CODE'"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'PREFIX=bar nvm_die_on_prefix 0 foo' did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "'PREFIX=bar nvm_die_on_prefix 0 foo' did not exit with 3; got '$CAPTURED_EXIT_CODE'"

-OUTPUT="$(export NPM_CONFIG_PREFIX=bar ; nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" 2>&1)"
+NPM_CONFIG_PREFIX=bar try_err nvm_die_on_prefix 0 foo "$(nvm_version_dir new)"
+unset NPM_CONFIG_PREFIX
 EXPECTED_OUTPUT='nvm is not compatible with the "NPM_CONFIG_PREFIX" environment variable: currently set to "bar"
 Run `unset NPM_CONFIG_PREFIX` to unset it.'
-EXIT_CODE="$(export NPM_CONFIG_PREFIX=bar ; nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'NPM_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_4" ] || die "'NPM_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not exit with 4; got '$EXIT_CODE'"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'NPM_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_4" ] || die "'NPM_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not exit with 4; got '$CAPTURED_EXIT_CODE'"

-OUTPUT="$(export npm_CONFIG_PREFIX=bar ; nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" 2>&1)"
+npm_CONFIG_PREFIX=bar try_err nvm_die_on_prefix 0 foo "$(nvm_version_dir new)"
+unset npm_CONFIG_PREFIX
 EXPECTED_OUTPUT='nvm is not compatible with the "npm_CONFIG_PREFIX" environment variable: currently set to "bar"
 Run `unset npm_CONFIG_PREFIX` to unset it.'
-EXIT_CODE="$(export npm_CONFIG_PREFIX=bar ; nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'npm_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_4" ] || die "'npm_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not exit with 4; got '$EXIT_CODE'"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'npm_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_4" ] || die "'npm_CONFIG_PREFIX=bar nvm_die_on_prefix 0 foo' did not exit with 4; got '$CAPTURED_EXIT_CODE'"

 OUTPUT="$(export FOO='This contains NPM_CONFIG_PREFIX' ; nvm_die_on_prefix 0 foo "$(nvm_version_dir new)" 2>&1)"
 [ -z "$OUTPUT" ] || die "'nvm_die_on_prefix' was not a noop; got '$OUTPUT'"
@@ -101,23 +100,21 @@ OUTPUT="$(export FOO='This contains NPM_CONFIG_PREFIX' ; nvm_die_on_prefix 0 foo

  # project: prefix
  echo 'prefix=garbage' > .npmrc
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your project npmrc file ($(nvm_sanitize_path "${TEST_DIR}")/.npmrc)
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has prefix did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has prefix did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  # project: globalconfig
  echo 'globalconfig=garbage' > .npmrc
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your project npmrc file ($(nvm_sanitize_path "${TEST_DIR}")/.npmrc)
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has globalconfig did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with project .npmrc that has globalconfig did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  rm "${TEST_DIR}/.npmrc" || die '.npmrc could not be removed'

@@ -133,67 +130,61 @@ Run \`foo\` to unset it."

  # global: prefix
  echo 'prefix=garbage' > "${GLOBAL_NPMRC}"
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your global npmrc file ($(nvm_sanitize_path "${GLOBAL_NPMRC}"))
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has prefix did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has prefix did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  # global: globalconfig
  echo 'globalconfig=garbage' > "${GLOBAL_NPMRC}"
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your global npmrc file ($(nvm_sanitize_path "${GLOBAL_NPMRC}"))
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has globalconfig did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with global npmrc that has globalconfig did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  rm "${GLOBAL_NPMRC}" || die "${GLOBAL_NPMRC} could not be removed"

  # builtin: prefix
  echo 'prefix=garbage' > "${BUILTIN_NPMRC}"
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your builtin npmrc file ($(nvm_sanitize_path "${BUILTIN_NPMRC}"))
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has prefix did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has prefix did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  # builtin: globalconfig
  echo 'globalconfig=garbage' > "${BUILTIN_NPMRC}"
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your builtin npmrc file ($(nvm_sanitize_path "${BUILTIN_NPMRC}"))
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has globalconfig did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with builtin npmrc that has globalconfig did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  rm "${BUILTIN_NPMRC}" || die "${BUILTIN_NPMRC} could not be removed"

  # user: prefix
  echo 'prefix=garbage' > "${USER_NPMRC}"
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your user’s .npmrc file ($(nvm_sanitize_path "${USER_NPMRC}"))
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has prefix did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has prefix did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has prefix did not exit with 10; got '$CAPTURED_EXIT_CODE'"

  # user: globalconfig
  echo 'globalconfig=garbage' > "${USER_NPMRC}"
-  OUTPUT="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" 2>&1)"
+  try_err nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}"
  EXPECTED_OUTPUT="Your user’s .npmrc file ($(nvm_sanitize_path "${USER_NPMRC}"))
 has a \`globalconfig\` and/or a \`prefix\` setting, which are incompatible with nvm.
 Run \`foo\` to unset it."
-  EXIT_CODE="$(nvm_die_on_prefix 0 foo "${TEST_VERSION_DIR}" >/dev/null 2>&1; echo $?)"
-  [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-  [ "_$EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has globalconfig did not exit with 10; got '$EXIT_CODE'"
+  [ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has globalconfig did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+  [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has globalconfig did not exit with 10; got '$CAPTURED_EXIT_CODE'"
 )

 cleanup
--- a/tests/nvm_get_checksum
+++ b/tests/nvm_get_checksum
@@ -12,17 +12,16 @@ set +e # TODO: fix
 \. ../../../nvm.sh
 set -e

+\. ../../common.sh
+
 nvm_get_mirror() {
  echo "mirror-${1}-${2}"
 }

-set +ex # needed to capture error output
-OUTPUT="$(nvm_get_checksum 2>&1 >/dev/null)"
+try_err nvm_get_checksum
 EXPECTED_OUTPUT='supported flavors: node, iojs'
-EXIT_CODE="$(nvm_get_checksum >/dev/null 2>&1 ; echo $?)"
-set -ex
-[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected error output >${EXPECTED_OUTPUT}<, got >${OUTPUT}<"
-[ "${EXIT_CODE}" = 2 ] || die "expected exit code 2, got ${EXIT_CODE}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED_OUTPUT}" ] || die "expected error output >${EXPECTED_OUTPUT}<, got >${CAPTURED_STDERR}<"
+[ "${CAPTURED_EXIT_CODE}" = 2 ] || die "expected exit code 2, got ${CAPTURED_EXIT_CODE}"

 nvm_download() {
  echo "ERROR_FAILED_MATCH no_match more fields"
--- a/tests/nvm_get_latest
+++ b/tests/nvm_get_latest
@@ -9,13 +9,14 @@ cleanup() {
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 nvm_has() { return 1 ; }

-OUTPUT="$(nvm_get_latest 2>&1)"
-EXIT_CODE="$(nvm_get_latest >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_nvm needs curl or wget to proceed." ] \
-  || die "no curl/wget did not report correct error message, got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_1" ] \
-  || die "no curl/wget did not exit with code 1, got $EXIT_CODE"
+try_err nvm_get_latest
+[ "_$CAPTURED_STDERR" = "_nvm needs curl or wget to proceed." ] \
+  || die "no curl/wget did not report correct error message, got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] \
+  || die "no curl/wget did not exit with code 1, got $CAPTURED_EXIT_CODE"

 cleanup
--- a/tests/nvm_get_minor_version
+++ b/tests/nvm_get_minor_version
@@ -5,6 +5,8 @@ die () { echo "$@" ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 expect () {
  INPUT="$1"
  EXPECTED_OUTPUT="$2"
@@ -20,8 +22,8 @@ fail_with () {
  INPUT="$1"
  EXPECTED_CODE="$2"

-  EXIT_CODE="$(nvm_get_minor_version "$INPUT" >/dev/null 2>&1; echo $?)"
-  [ "_$EXIT_CODE" = "_$EXPECTED_CODE" ] || die "nvm_get_minor_version "$INPUT" did not fail with code "$EXPECTED_CODE"; got $EXIT_CODE"
+  try nvm_get_minor_version "$INPUT"
+  [ "_$CAPTURED_EXIT_CODE" = "_$EXPECTED_CODE" ] || die "nvm_get_minor_version "$INPUT" did not fail with code "$EXPECTED_CODE"; got $CAPTURED_EXIT_CODE"
 }

 expect 1 1.0
--- a/tests/nvm_install_latest_npm
+++ b/tests/nvm_install_latest_npm
@@ -22,11 +22,10 @@ npm() {
  echo '1.2.3'
 }

-OUTPUT="$(nvm_install_latest_npm 2>&1 >/dev/null)"
-EXIT_CODE="$(nvm_install_latest_npm >/dev/null 2>&1 ; echo $?)"
+try_err nvm_install_latest_npm

 EXPECTED="Unable to obtain node version."
-[ "${OUTPUT}" = "${EXPECTED}" ] || die "When node is unavailable, expected >${EXPECTED}<; got >${OUTPUT}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED}" ] || die "When node is unavailable, expected >${EXPECTED}<; got >${CAPTURED_STDERR}"

 node() {
  echo 'v4.5.6'
@@ -37,11 +36,10 @@ nvm_ls_current() {
 npm() {
  return 1
 }
-OUTPUT="$(nvm_install_latest_npm 2>&1 >/dev/null)"
-EXIT_CODE="$(nvm_install_latest_npm >/dev/null 2>&1 ; echo $?)"
+try_err nvm_install_latest_npm

 EXPECTED="Unable to obtain npm version."
-[ "${OUTPUT}" = "${EXPECTED}" ] || die "When node is available and npm is unavailable, expected >${EXPECTED}<; got >${OUTPUT}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED}" ] || die "When node is available and npm is unavailable, expected >${EXPECTED}<; got >${CAPTURED_STDERR}"

 node() {
  echo 'v4.5.6'
@@ -52,8 +50,7 @@ nvm_ls_current() {
 npm() {
  return 1
 }
-OUTPUT="$(nvm_install_latest_npm 2>&1 >/dev/null)"
-EXIT_CODE="$(nvm_install_latest_npm >/dev/null 2>&1 ; echo $?)"
+try_err nvm_install_latest_npm

 EXPECTED="Unable to obtain npm version."
-[ "${OUTPUT}" = "${EXPECTED}" ] || die "When node is system and npm is unavailable, expected >${EXPECTED}<; got >${OUTPUT}"
+[ "${CAPTURED_STDERR}" = "${EXPECTED}" ] || die "When node is system and npm is unavailable, expected >${EXPECTED}<; got >${CAPTURED_STDERR}"
--- a/tests/nvm_ls_remote
+++ b/tests/nvm_ls_remote
@@ -19,10 +19,11 @@ nvm_download() {

 EXPECTED_OUTPUT_PATH="$MOCKS_DIR/nvm_ls_remote.txt"

-OUTPUT="$(nvm_ls_remote foo)"
-EXIT_CODE="$(nvm_ls_remote foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+\. ../../common.sh
+
+try nvm_ls_remote foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"

 OUTPUT="$(nvm_ls_remote)"
 EXPECTED_OUTPUT="$(cat "$EXPECTED_OUTPUT_PATH")"
--- a/tests/nvm_ls_remote
+++ b/tests/nvm_ls_remote
@@ -19,10 +19,11 @@ nvm_download() {

 EXPECTED_OUTPUT_PATH="$MOCKS_DIR/nvm_ls_remote nightly.txt"

-OUTPUT="$(nvm_ls_remote foo)"
-EXIT_CODE="$(nvm_ls_remote foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+\. ../../common.sh
+
+try nvm_ls_remote foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"

 OUTPUT="$(nvm_ls_remote)"
 EXPECTED_OUTPUT="$(cat "$EXPECTED_OUTPUT_PATH")"
--- a/tests/nvm_ls_remote_iojs
+++ b/tests/nvm_ls_remote_iojs
@@ -17,10 +17,11 @@ nvm_download() {

 EXPECTED_OUTPUT_PATH="$PWD/mocks/nvm_ls_remote_iojs.txt"

-OUTPUT="$(nvm_ls_remote_iojs foo)"
-EXIT_CODE="$(nvm_ls_remote_iojs foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+\. ../../common.sh
+
+try nvm_ls_remote_iojs foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"

 OUTPUT="$(nvm_ls_remote_iojs)"
 EXPECTED_OUTPUT="$(cat "$EXPECTED_OUTPUT_PATH")"
--- a/tests/nvm_make_alias
+++ b/tests/nvm_make_alias
@@ -5,16 +5,16 @@ die () { echo "$@" ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh

-OUTPUT="$(nvm_make_alias 2>&1)"
-EXIT_CODE="$(nvm_make_alias >/dev/null 2>&1 ; echo $?)"
+\. ../../common.sh
+
+try_err nvm_make_alias
 EXPECTED_OUTPUT='an alias name is required'

-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "\`nvm_make_alias\` did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "$EXIT_CODE" -eq 1 ] || die "\`nvm_make_alias\` did not exit with 1, got '$EXIT_CODE'"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "\`nvm_make_alias\` did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" -eq 1 ] || die "\`nvm_make_alias\` did not exit with 1, got '$CAPTURED_EXIT_CODE'"

-OUTPUT="$(nvm_make_alias foo 2>&1)"
-EXIT_CODE="$(nvm_make_alias foo >/dev/null 2>&1 ; echo $?)"
+try_err nvm_make_alias foo
 EXPECTED_OUTPUT='an alias target version is required'

-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "\`nvm_make_alias foo\` did not error with '$EXPECTED_OUTPUT'; got '$OUTPUT'"
-[ "$EXIT_CODE" -eq 2 ] || die "\`nvm_make_alias foo\` did not exit with 2, got '$EXIT_CODE'"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "\`nvm_make_alias foo\` did not error with '$EXPECTED_OUTPUT'; got '$CAPTURED_STDERR'"
+[ "$CAPTURED_EXIT_CODE" -eq 2 ] || die "\`nvm_make_alias foo\` did not exit with 2, got '$CAPTURED_EXIT_CODE'"
--- a/tests/nvm_print_alias_path
+++ b/tests/nvm_print_alias_path
@@ -24,12 +24,11 @@ nvm_alias() {
  echo ''
 }

-OUTPUT="$(nvm_print_alias_path "$NVM_ALIAS_DIR" foo | strip_colors)"
+try nvm_print_alias_path "$NVM_ALIAS_DIR" foo
+OUTPUT="$(echo "$CAPTURED_STDOUT" | strip_colors)"
 EXPECTED_OUTPUT=''
 [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_print_alias_path \"\$NVM_ALIAS_DIR\" foo' should produce no output when nvm_alias does not; got '$OUTPUT'"
-
-EXIT_CODE="$(nvm_print_alias_path "$NVM_ALIAS_DIR" foo >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = '0' ] || die "'nvm_print_alias_path \"\$NVM_ALIAS_DIR\" foo' should exit zero when nvm_alias produces no output; got $EXIT_CODE"
+[ "$CAPTURED_EXIT_CODE" = '0' ] || die "'nvm_print_alias_path \"\$NVM_ALIAS_DIR\" foo' should exit zero when nvm_alias produces no output; got $CAPTURED_EXIT_CODE"

 nvm_alias() {
  echo "\"$1\""
--- a/tests/nvm_print_default_alias
+++ b/tests/nvm_print_default_alias
@@ -18,12 +18,11 @@ OUTPUT="$(nvm_print_default_alias 2>&1)"
 EXPECTED_OUTPUT='A default alias is required.'
 [ "$OUTPUT" = "$EXPECTED_OUTPUT" ] || die "'nvm_print_default_alias' produced wrong output; got '$OUTPUT', expected '$EXPECTED_OUTPUT'"

-OUTPUT="$(nvm_print_default_alias foo | strip_colors)"
+try nvm_print_default_alias foo
+OUTPUT="$(echo "$CAPTURED_STDOUT" | strip_colors)"
 EXPECTED_OUTPUT=''
 [ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "'nvm_print_default_alias foo' should produce no output when nvm_print_implicit_alias does not; got '$OUTPUT'"
-
-EXIT_CODE="$(nvm_print_default_alias foo >/dev/null 2>&1 ; echo $?)"
-[ "$EXIT_CODE" = '0' ] || die "'nvm_print_default_alias foo' should exit zero when nvm_print_implicit_alias produces no output; got $EXIT_CODE"
+[ "$CAPTURED_EXIT_CODE" = '0' ] || die "'nvm_print_default_alias foo' should exit zero when nvm_print_implicit_alias produces no output; got $CAPTURED_EXIT_CODE"

 nvm_print_implicit_alias() {
  echo "\"$1-$2\""
--- a/tests/nvm_print_implicit_alias
+++ b/tests/nvm_print_implicit_alias
@@ -5,15 +5,17 @@ die () { echo "$@" ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 EXPECTED_FIRST_MSG="nvm_print_implicit_alias must be specified with local or remote as the first argument."
 [ "_$(nvm_print_implicit_alias 2>&1)" = "_$EXPECTED_FIRST_MSG" ] \
  || die "nvm_print_implicit_alias did not require local|remote as first argument"
 [ "_$(nvm_print_implicit_alias foo 2>&1)" = "_$EXPECTED_FIRST_MSG" ] \
  || die "nvm_print_implicit_alias did not require local|remote as first argument"

-FIRST_EXIT_CODE="$(nvm_print_implicit_alias > /dev/null 2>&1 ; echo $?)"
-[ "_$FIRST_EXIT_CODE" = "_1" ] \
-  || die "nvm_print_implicit_alias without local|remote had wrong exit code: expected 1, got $FIRST_EXIT_CODE"
+try_err nvm_print_implicit_alias
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] \
+  || die "nvm_print_implicit_alias without local|remote had wrong exit code: expected 1, got $CAPTURED_EXIT_CODE"

 EXPECTED_SECOND_MSG="Only implicit aliases 'stable', 'unstable', 'iojs', and 'node' are supported."
 [ "_$(nvm_print_implicit_alias local 2>&1)" = "_$EXPECTED_SECOND_MSG" ] \
@@ -21,6 +23,6 @@ EXPECTED_SECOND_MSG="Only implicit aliases 'stable', 'unstable', 'iojs', and 'no
 [ "_$(nvm_print_implicit_alias local foo 2>&1)" = "_$EXPECTED_SECOND_MSG" ] \
  || die "nvm_print_implicit_alias did not require stable|unstable|iojs|node as second argument"

-SECOND_EXIT_CODE="$(nvm_print_implicit_alias local > /dev/null 2>&1 ; echo $?)"
-[ "_$SECOND_EXIT_CODE" = "_2" ] \
-  || die "nvm_print_implicit_alias without stable|unstable|iojs|node had wrong exit code: expected 2, got $SECOND_EXIT_CODE"
+try_err nvm_print_implicit_alias local
+[ "_$CAPTURED_EXIT_CODE" = "_2" ] \
+  || die "nvm_print_implicit_alias without stable|unstable|iojs|node had wrong exit code: expected 2, got $CAPTURED_EXIT_CODE"
--- a/tests/nvm_process_nvmrc
+++ b/tests/nvm_process_nvmrc
@@ -12,24 +12,23 @@ cleanup() {
 \. ../../common.sh

 for f in ../../../test/fixtures/nvmrc/test/fixtures/valid/*; do
-  STDOUT="$(nvm_process_nvmrc $f/.nvmrc 2>/dev/null)"
-  EXIT_CODE="$(nvm_process_nvmrc $f/.nvmrc >/dev/null 2>/dev/null; echo $?)"
+  try nvm_process_nvmrc $f/.nvmrc

  EXPECTED="$(nvm_json_extract node < "${f}/expected.json" | tr -d '"')"

-  [ "${EXIT_CODE}" = "0" ] || die "$(basename "${f}"): expected exit code of 0 but got ${EXIT_CODE}"
+  [ "${CAPTURED_EXIT_CODE}" = "0" ] || die "$(basename "${f}"): expected exit code of 0 but got ${CAPTURED_EXIT_CODE}"

-  [ "${STDOUT}" = "${EXPECTED}" ] || die "$(basename "${f}"): expected STDOUT of \`${EXPECTED}\` but got \`${STDOUT}\`"
+  [ "${CAPTURED_STDOUT}" = "${EXPECTED}" ] || die "$(basename "${f}"): expected STDOUT of \`${EXPECTED}\` but got \`${CAPTURED_STDOUT}\`"
 done

 for f in ../../../test/fixtures/nvmrc/test/fixtures/invalid/*; do
-  STDOUT="$(nvm_process_nvmrc $f/.nvmrc 2>/dev/null)"
-  STDERR="$(nvm_process_nvmrc $f/.nvmrc 2>&1 >/dev/null | awk '{if(NR > 8) print $0}' | strip_colors)"
-  EXIT_CODE="$(nvm_process_nvmrc $f/.nvmrc >/dev/null 2>/dev/null; echo $?)"
+  try nvm_process_nvmrc $f/.nvmrc
+  try_err nvm_process_nvmrc $f/.nvmrc
+  STDERR="$(echo "$CAPTURED_STDERR" | awk '{if(NR > 8) print $0}' | strip_colors)"

  EXPECTED="$(nvm_json_extract < "${f}/expected.json" | tr -d '"')"

-  [ "${EXIT_CODE}" != "0" ] || die "$(basename "${f}"): expected exit code of 'not 0' but got ${EXIT_CODE}"
+  [ "${CAPTURED_EXIT_CODE}" != "0" ] || die "$(basename "${f}"): expected exit code of 'not 0' but got ${CAPTURED_EXIT_CODE}"

  [ "${STDERR}" = "${EXPECTED}" ] || die "$(basename "${f}"): expected STDERR of \`${EXPECTED}\` but got \`${STDERR}\`"
 done
--- a/tests/nvm_remote_version
+++ b/tests/nvm_remote_version
@@ -9,21 +9,21 @@ cleanup() {
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 nvm_ls_remote() {
  echo "N/A"
 }
-OUTPUT="$(nvm_remote_version foo)"
-EXIT_CODE="$(nvm_remote_version foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+try nvm_remote_version foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"

 nvm_ls_remote_iojs() {
  echo "N/A"
 }
-OUTPUT="$(nvm_remote_version iojs-foo)"
-EXIT_CODE="$(nvm_remote_version iojs-foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+try nvm_remote_version iojs-foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"


 nvm_ls_remote() {
@@ -40,41 +40,35 @@ nvm_ls_remote_iojs() {
    echo "iojs_pattern_received:_$1_"
  fi
 }
-OUTPUT="$(nvm_remote_version foo)"
-EXIT_CODE="$(nvm_remote_version foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_pattern_received:_foo_" ] \
-  || die "nvm_remote_version foo did not return last line only of nvm_ls_remote foo; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version foo did not exit with 0, got $EXIT_CODE"
+try nvm_remote_version foo
+[ "_$CAPTURED_STDOUT" = "_pattern_received:_foo_" ] \
+  || die "nvm_remote_version foo did not return last line only of nvm_ls_remote foo; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version foo did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_version iojs-foo)"
-EXIT_CODE="$(nvm_remote_version iojs-foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_iojs_pattern_received:_iojs-foo_" ] \
-  || die "nvm_remote_version iojs-foo did not return last line only of nvm_ls_remote_iojs foo; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version iojs-foo did not exit with 0, got $EXIT_CODE"
+try nvm_remote_version iojs-foo
+[ "_$CAPTURED_STDOUT" = "_iojs_pattern_received:_iojs-foo_" ] \
+  || die "nvm_remote_version iojs-foo did not return last line only of nvm_ls_remote_iojs foo; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version iojs-foo did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_version iojs)"
-EXIT_CODE="$(nvm_remote_version iojs >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_iojs_pattern_received:__" ] \
-  || die "nvm_remote_version iojs did not return last line only of nvm_ls_remote_iojs; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version iojs did not exit with 0, got $EXIT_CODE"
+try nvm_remote_version iojs
+[ "_$CAPTURED_STDOUT" = "_iojs_pattern_received:__" ] \
+  || die "nvm_remote_version iojs did not return last line only of nvm_ls_remote_iojs; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version iojs did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_version stable)"
-EXIT_CODE="$(nvm_remote_version stable >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote stable)" ] \
-  || die "nvm_remote_version stable did not return contents of nvm_ls_remote stable; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version stable did not exit with 0, got $EXIT_CODE"
+try nvm_remote_version stable
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote stable)" ] \
+  || die "nvm_remote_version stable did not return contents of nvm_ls_remote stable; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version stable did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_version unstable)"
-EXIT_CODE="$(nvm_remote_version unstable >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote unstable)" ] \
-  || die "nvm_remote_version unstable did not return contents of nvm_ls_remote unstable; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version unstable did not exit with 0, got $EXIT_CODE"
+try nvm_remote_version unstable
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote unstable)" ] \
+  || die "nvm_remote_version unstable did not return contents of nvm_ls_remote unstable; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version unstable did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_version node)"
-EXIT_CODE="$(nvm_remote_version node >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote node)" ] \
-  || die "nvm_remote_version node did not return contents of nvm_ls_remote node; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version node did not exit with 0, got $EXIT_CODE"
+try nvm_remote_version node
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote node)" ] \
+  || die "nvm_remote_version node did not return contents of nvm_ls_remote node; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version node did not exit with 0, got $CAPTURED_EXIT_CODE"

 # Test LTS name rejection (Issue #3474)
 # When nvm_remote_versions returns a line with LTS name in description,
@@ -83,17 +77,15 @@ EXIT_CODE="$(nvm_remote_version node >/dev/null 2>&1 ; echo $?)"
 nvm_remote_versions() {
    echo "v4.9.1 Argon *"
 }
-OUTPUT="$(nvm_remote_version Argon)"
-EXIT_CODE="$(nvm_remote_version Argon >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nvm_remote_version Argon should return N/A (LTS name not in version), got $OUTPUT"
-[ "_$EXIT_CODE" = "_3" ] || die "nvm_remote_version Argon should exit with code 3, got $EXIT_CODE"
+try nvm_remote_version Argon
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nvm_remote_version Argon should return N/A (LTS name not in version), got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nvm_remote_version Argon should exit with code 3, got $CAPTURED_EXIT_CODE"

 nvm_remote_versions() {
  echo "v4.9.1"
 }
-OUTPUT="$(nvm_remote_version 4)"
-EXIT_CODE="$(nvm_remote_version 4 >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_v4.9.1" ] || die "nvm_remote_version 4 should return v4.9.1, got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version 4 should exit with code 0, got $EXIT_CODE"
+try nvm_remote_version 4
+[ "_$CAPTURED_STDOUT" = "_v4.9.1" ] || die "nvm_remote_version 4 should return v4.9.1, got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_version 4 should exit with code 0, got $CAPTURED_EXIT_CODE"

 cleanup
--- a/tests/nvm_remote_versions
+++ b/tests/nvm_remote_versions
@@ -9,33 +9,31 @@ cleanup() {
 : nvm.sh
 \. ../../../nvm.sh

-OUTPUT="$(nvm_remote_versions stable 2>&1)"
-EXPECTED_OUTPUT="Implicit aliases are not supported in nvm_remote_versions."
-EXIT_CODE="$(nvm_remote_versions stable >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "implicit alias 'stable' did not error out with correct message, got $OUTPUT"
-[ "_$EXIT_CODE" = "_1" ] || die "implicit alias 'stable' did not exit with code 1, got $EXIT_CODE"
+\. ../../common.sh

-OUTPUT="$(nvm_remote_versions unstable 2>&1)"
+try_err nvm_remote_versions stable
 EXPECTED_OUTPUT="Implicit aliases are not supported in nvm_remote_versions."
-EXIT_CODE="$(nvm_remote_versions unstable >/dev/null 2>&1; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die "implicit alias 'unstable' did not error out with correct message, got $OUTPUT"
-[ "_$EXIT_CODE" = "_1" ] || die "implicit alias 'unstable' did not exit with code 1, got $EXIT_CODE"
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "implicit alias 'stable' did not error out with correct message, got $CAPTURED_STDERR"
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] || die "implicit alias 'stable' did not exit with code 1, got $CAPTURED_EXIT_CODE"
+
+try_err nvm_remote_versions unstable
+EXPECTED_OUTPUT="Implicit aliases are not supported in nvm_remote_versions."
+[ "_$CAPTURED_STDERR" = "_$EXPECTED_OUTPUT" ] || die "implicit alias 'unstable' did not error out with correct message, got $CAPTURED_STDERR"
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] || die "implicit alias 'unstable' did not exit with code 1, got $CAPTURED_EXIT_CODE"

 nvm_ls_remote() {
  echo "N/A"
 }
-OUTPUT="$(nvm_remote_versions foo)"
-EXIT_CODE="$(nvm_remote_versions foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+try nvm_remote_versions foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"

 nvm_ls_remote_iojs() {
  echo "N/A"
 }
-OUTPUT="$(nvm_remote_versions iojs-foo)"
-EXIT_CODE="$(nvm_remote_versions iojs-foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_N/A" ] || die "nonexistent version did not report N/A"
-[ "_$EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $EXIT_CODE"
+try nvm_remote_versions iojs-foo
+[ "_$CAPTURED_STDOUT" = "_N/A" ] || die "nonexistent version did not report N/A"
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die "nonexistent version did not exit with code 3, got $CAPTURED_EXIT_CODE"


 nvm_ls_remote() {
@@ -49,30 +47,26 @@ nvm_ls_remote_iojs() {
  echo "iojs pattern received: _$1_"
 }

-OUTPUT="$(nvm_remote_versions foo)"
-EXIT_CODE="$(nvm_remote_versions foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote foo)
+try nvm_remote_versions foo
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote foo)
 $(nvm_ls_remote_iojs foo)" ] \
-  || die "nvm_remote_versions foo did not return contents of nvm_ls_remote foo combined with nvm_ls_remote_iojs foo; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_versions foo did not exit with 0, got $EXIT_CODE"
+  || die "nvm_remote_versions foo did not return contents of nvm_ls_remote foo combined with nvm_ls_remote_iojs foo; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_versions foo did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_versions node)"
-EXIT_CODE="$(nvm_remote_versions node >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote)" ] \
-  || die "nvm_remote_versions node did not return contents of nvm_ls_remote; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_versions node did not exit with 0, got $EXIT_CODE"
+try nvm_remote_versions node
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote)" ] \
+  || die "nvm_remote_versions node did not return contents of nvm_ls_remote; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_versions node did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_versions iojs-foo)"
-EXIT_CODE="$(nvm_remote_versions iojs-foo >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote iojs-foo)
+try nvm_remote_versions iojs-foo
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote iojs-foo)
 $(nvm_ls_remote_iojs iojs-foo)" ] \
-  || die "nvm_remote_versions iojs-foo did not return contents of nvm_ls_remote iojs-foo combined with nvm_ls_remote_iojs iojs-foo; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_versions iojs-foo did not exit with 0, got $EXIT_CODE"
+  || die "nvm_remote_versions iojs-foo did not return contents of nvm_ls_remote iojs-foo combined with nvm_ls_remote_iojs iojs-foo; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_versions iojs-foo did not exit with 0, got $CAPTURED_EXIT_CODE"

-OUTPUT="$(nvm_remote_versions iojs)"
-EXIT_CODE="$(nvm_remote_versions iojs >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$(nvm_ls_remote_iojs)" ] \
-  || die "nvm_remote_versions iojs did not return contents of nvm_ls_remote_iojs; got $OUTPUT"
-[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_versions iojs did not exit with 0, got $EXIT_CODE"
+try nvm_remote_versions iojs
+[ "_$CAPTURED_STDOUT" = "_$(nvm_ls_remote_iojs)" ] \
+  || die "nvm_remote_versions iojs did not return contents of nvm_ls_remote_iojs; got $CAPTURED_STDOUT"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] || die "nvm_remote_versions iojs did not exit with 0, got $CAPTURED_EXIT_CODE"

 cleanup
--- a/tests/nvm_validate_implicit_alias
+++ b/tests/nvm_validate_implicit_alias
@@ -5,15 +5,17 @@ die () { echo "$@" ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 EXPECTED_MSG="Only implicit aliases 'stable', 'unstable', 'iojs', and 'node' are supported."
 [ "_$(nvm_validate_implicit_alias 2>&1)" = "_$EXPECTED_MSG" ] \
  || die "nvm_validate_implicit_alias did not require stable|unstable|iojs|node"
 [ "_$(nvm_validate_implicit_alias foo 2>&1)" = "_$EXPECTED_MSG" ] \
  || die "nvm_validate_implicit_alias did not require stable|unstable|iojs|node"

-EXIT_CODE="$(nvm_validate_implicit_alias >/dev/null 2>&1 ; echo $?)"
-[ "_$EXIT_CODE" = "_1" ] \
-  || die "nvm_validate_implicit_alias without stable|unstable|iojs|node had wrong exit code: expected 1, got $EXIT_CODE"
+try_err nvm_validate_implicit_alias
+[ "_$CAPTURED_EXIT_CODE" = "_1" ] \
+  || die "nvm_validate_implicit_alias without stable|unstable|iojs|node had wrong exit code: expected 1, got $CAPTURED_EXIT_CODE"

 nvm_validate_implicit_alias stable || die "nvm_validate_implicit_alias stable did not exit 0"
 nvm_validate_implicit_alias unstable || die "nvm_validate_implicit_alias unstable did not exit 0"
--- a/tests/nvm_version
+++ b/tests/nvm_version
@@ -8,22 +8,22 @@ cleanup () {
 : nvm.sh
 \. ../../../nvm.sh

+\. ../../common.sh
+
 nvm_ls_current() {
  echo "CURRENT!"
  return 7
 }

-OUTPUT="$(nvm_version current)"
+try nvm_version current
 EXPECTED_OUTPUT="CURRENT!"
-EXIT_CODE="$(nvm_version current 2>&1 >/dev/null ; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version current" did not return nvm_ls_current output'
-[ "_$EXIT_CODE" = "_7" ] || die '"nvm_version current" did not return nvm_ls_current exit code'
+[ "_$CAPTURED_STDOUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version current" did not return nvm_ls_current output'
+[ "_$CAPTURED_EXIT_CODE" = "_7" ] || die '"nvm_version current" did not return nvm_ls_current exit code'

-OUTPUT="$(nvm_version)"
+try nvm_version
 EXPECTED_OUTPUT="CURRENT!"
-EXIT_CODE="$(nvm_version 2>&1 >/dev/null ; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version" did not return nvm_ls_current output'
-[ "_$EXIT_CODE" = "_7" ] || die '"nvm_version" did not return nvm_ls_current exit code'
+[ "_$CAPTURED_STDOUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version" did not return nvm_ls_current output'
+[ "_$CAPTURED_EXIT_CODE" = "_7" ] || die '"nvm_version" did not return nvm_ls_current exit code'

 nvm_ls() {
  echo "line 1"
@@ -38,15 +38,13 @@ nvm_ls() { echo "system v20.0.0"; }
 [ "_$(nvm_version system)" = "_system" ] || die '"nvm_version system" did not return "system" when "nvm_ls" returns extra columns'

 nvm_ls() { echo "N/A"; }
-OUTPUT="$(nvm_version foo)"
+try nvm_version foo
 EXPECTED_OUTPUT="N/A"
-EXIT_CODE="$(nvm_version foo 2>&1 >/dev/null ; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version" did not return N/A when nvm_ls returns N/A'
-[ "_$EXIT_CODE" = "_3" ] || die '"nvm_version" returning N/A did not exit code with code 3'
+[ "_$CAPTURED_STDOUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version" did not return N/A when nvm_ls returns N/A'
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die '"nvm_version" returning N/A did not exit code with code 3'

 nvm_ls() { echo; }
-OUTPUT="$(nvm_version foo)"
+try nvm_version foo
 EXPECTED_OUTPUT="N/A"
-EXIT_CODE="$(nvm_version foo 2>&1 >/dev/null ; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version" did not return N/A when nvm_ls returns nothing'
-[ "_$EXIT_CODE" = "_3" ] || die '"nvm_version" returning N/A did not exit code with code 3'
+[ "_$CAPTURED_STDOUT" = "_$EXPECTED_OUTPUT" ] || die '"nvm_version" did not return N/A when nvm_ls returns nothing'
+[ "_$CAPTURED_EXIT_CODE" = "_3" ] || die '"nvm_version" returning N/A did not exit code with code 3'
--- a/test/slow/nvm
+++ b/test/slow/nvm
@@ -4,6 +4,8 @@ die () { echo "$@" ; exit 1; }

 \. ../../../nvm.sh

+\. ../../common.sh
+
 nvm deactivate >/dev/null 2>&1 || die 'deactivate failed'

 nvm_die_on_prefix() {
@@ -11,12 +13,12 @@ nvm_die_on_prefix() {
  return 3
 }

-OUTPUT="$(nvm use --silent node)"
+try nvm use --silent node
 EXPECTED_OUTPUT=""
-[ "_$OUTPUT" = "_$EXPECTED_OUTPUT" ] \
-  || die "'nvm use --silent node' did not call through to 'nvm_die_on_prefix' and give output '$EXPECTED_OUTPUT'; got '$OUTPUT'"
+[ "_$CAPTURED_STDOUT" = "_$EXPECTED_OUTPUT" ] \
+  || die "'nvm use --silent node' did not call through to 'nvm_die_on_prefix' and give output '$EXPECTED_OUTPUT'; got '$CAPTURED_STDOUT'"

-EXIT_CODE="$(nvm use --silent node >/dev/null 2>&1; echo $?)"
+try_err nvm use --silent node
 EXPECTED_CODE="11"
-[ "_$EXIT_CODE" = "_$EXPECTED_CODE" ] \
-  || die "'nvm use --silent node' when 'nvm_die_on_prefix' fails did not return '$EXPECTED_CODE'; got '$EXIT_CODE'"
+[ "_$CAPTURED_EXIT_CODE" = "_$EXPECTED_CODE" ] \
+  || die "'nvm use --silent node' when 'nvm_die_on_prefix' fails did not return '$EXPECTED_CODE'; got '$CAPTURED_EXIT_CODE'"
--- a/test/slow/nvm_get_latest/nvm_get_latest
+++ b/test/slow/nvm_get_latest/nvm_get_latest
@@ -90,12 +90,13 @@ wget() {
  fi
 }

-OUTPUT="$(nvm_get_latest)"
-EXIT_CODE="$(nvm_get_latest >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_$EXPECTED_VERSION" ] \
-  || die "success path did not return version '$EXPECTED_VERSION', got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_0" ] \
-  || die "success path did not exit with code 0, got $EXIT_CODE"
+\. ../../common.sh
+
+try nvm_get_latest
+[ "_$CAPTURED_STDOUT" = "_$EXPECTED_VERSION" ] \
+  || die "success path did not return version '$EXPECTED_VERSION', got '$CAPTURED_STDOUT'"
+[ "_$CAPTURED_EXIT_CODE" = "_0" ] \
+  || die "success path did not exit with code 0, got $CAPTURED_EXIT_CODE"


 cleanup
--- a/test/slow/nvm_get_latest/nvm_get_latest
+++ b/test/slow/nvm_get_latest/nvm_get_latest
@@ -8,6 +8,8 @@ cleanup() {

 \. ../../../nvm.sh

+\. ../../common.sh
+
 curl() {
  return 1
 }
@@ -15,11 +17,10 @@ wget() {
  return 1
 }

-OUTPUT="$(nvm_get_latest 2>&1)"
-EXIT_CODE="$(nvm_get_latest >/dev/null 2>&1 ; echo $?)"
-[ "_$OUTPUT" = "_https://latest.nvm.sh did not redirect to the latest release on GitHub" ] \
-  || die "failed redirect did not report correct error message, got '$OUTPUT'"
-[ "_$EXIT_CODE" = "_2" ] \
-  || die "failed redirect did not exit with code 2, got $EXIT_CODE"
+try_err nvm_get_latest
+[ "_$CAPTURED_STDERR" = "_https://latest.nvm.sh did not redirect to the latest release on GitHub" ] \
+  || die "failed redirect did not report correct error message, got '$CAPTURED_STDERR'"
+[ "_$CAPTURED_EXIT_CODE" = "_2" ] \
+  || die "failed redirect did not exit with code 2, got $CAPTURED_EXIT_CODE"

 cleanup