diff --git a/.github/workflows/pyenv_tests.yml b/.github/workflows/pyenv_tests.yml
new file mode 100644
index 00000000..5eb275b8
--- /dev/null
+++ b/.github/workflows/pyenv_tests.yml
@@ -0,0 +1,35 @@
+name: pyenv_tests
+on: [pull_request, push]
+jobs:
+  pyenv_tests:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-20.04
+          - ubuntu-18.04
+          - macos-11
+          - macos-10.15
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2
+      # Normally, we would use the superbly maintained...
+      # - uses: actions/setup-python@v2
+      #   with:
+      #    python-version: ${{ matrix.python-version }}
+      # ... but in the repo, we want to test pyenv builds on Ubuntu
+      # - run: |
+          # sudo apt-get install -y build-essential libssl-dev zlib1g-dev libbz2-dev \
+              # libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
+              # xz-utils tk-dev libffi-dev liblzma-dev python-openssl git
+      # https://github.com/pyenv/pyenv#installation
+      - run: |
+          if test "$RUNNER_OS" == "macOS"; then brew install coreutils; fi
+      - run: pwd
+      - env:
+          PYENV_ROOT: /home/runner/work/pyenv/pyenv
+        run: |
+          echo $PYENV_ROOT
+          echo "$PYENV_ROOT/shims:$PYENV_ROOT/bin" >> $GITHUB_PATH
+      - run: |
+          make test
diff --git a/libexec/pyenv-help b/libexec/pyenv-help
index 91962576..d89c0ffb 100755
--- a/libexec/pyenv-help
+++ b/libexec/pyenv-help
@@ -44,8 +44,9 @@ extract_initial_comment_block() {
 }
 
 collect_documentation() {
-  # shellcheck disable=SC2016
-  $(type -P gawk awk | head -1) '
+  # `tail` prevents "broken pipe" errors due to `head` closing thge pipe without reading everything
+  # https://superuser.com/questions/554855/how-can-i-fix-a-broken-pipe-error/642932#642932
+  $(type -P gawk awk | tail -n +1 | head -1) '
     /^Summary:/ {
       summary = substr($0, 10)
       next
diff --git a/plugins/python-build/test/build.bats b/plugins/python-build/test/build.bats
index 3113b37b..e2f95331 100644
--- a/plugins/python-build/test/build.bats
+++ b/plugins/python-build/test/build.bats
@@ -160,17 +160,15 @@ OUT
   brew_libdir="$TMP/homebrew-yaml"
   mkdir -p "$brew_libdir"
 
-  # pyenv/pyenv#1026
-  stub uname false false
-
-  stub uname '-s : echo Linux'
-  stub uname '-s : echo Darwin'
+  for i in {1..4}; do stub uname '-s : echo Darwin'; done
+  for i in {1..2}; do stub sw_vers '-productVersion : echo 1010'; done
   stub brew "--prefix libyaml : echo '$brew_libdir'" false false
   stub_make_install
 
   install_fixture definitions/needs-yaml
   assert_success
 
+  unstub sw_vers
   unstub uname
   unstub brew
   unstub make
diff --git a/plugins/python-build/test/compiler.bats b/plugins/python-build/test/compiler.bats
index 0d426e0c..df813056 100644
--- a/plugins/python-build/test/compiler.bats
+++ b/plugins/python-build/test/compiler.bats
@@ -63,13 +63,9 @@ DEF
   mkdir -p "$INSTALL_ROOT"
   cd "$INSTALL_ROOT"
 
-  # pyenv/pyenv#1026
-  stub uname false '-s : echo Darwin' false '-s : echo Darwin' '-s : echo Darwin'
-  stub sw_vers '-productVersion : echo 10.10'
+  for i in {1..5}; do stub uname '-s : echo Darwin'; done
+  for i in {1..4}; do stub sw_vers '-productVersion : echo 10.10'; done
 
-  stub sw_vers '-productVersion : echo 10.10'
-  stub sw_vers '-productVersion : echo 10.10'
-  stub sw_vers '-productVersion : echo 10.10'
   stub cc 'false'
   stub brew 'false'
   stub make \
diff --git a/plugins/python-build/test/pyenv_ext.bats b/plugins/python-build/test/pyenv_ext.bats
index e4453113..9afb0ac7 100644
--- a/plugins/python-build/test/pyenv_ext.bats
+++ b/plugins/python-build/test/pyenv_ext.bats
@@ -136,7 +136,7 @@ OUT
 @test "apply built-in python patches should be sorted by its name" {
   cached_tarball "Python-3.6.2"
 
-  stub brew false
+  for i in {1..2}; do stub brew '* : false'; done
   stub_make_install
   stub patch ' : for arg; do [[ "$arg" == "-"* ]] || sed -e "s/^/patch: /" "$arg"; done >> build.log'
 
@@ -144,9 +144,7 @@ OUT
   echo "bar" | install_patch definitions/vanilla-python "Python-3.6.2/bar.patch"
   echo "baz" | install_patch definitions/vanilla-python "Python-3.6.2/baz.patch"
 
-  # yyuu/pyenv#257
-  stub uname '-s : echo Linux'
-  stub uname '-s : echo Linux'
+  for i in {1..2}; do stub uname '-s : echo Linux'; done
 
   TMPDIR="$TMP" install_tmp_fixture definitions/vanilla-python < /dev/null
   assert_success
@@ -173,9 +171,7 @@ OUT
     " : echo \"$MAKE \$@\" >> build.log" \
     " : echo \"$MAKE \$@\" >> build.log && cat build.log >> '$INSTALL_ROOT/build.log'"
 
-  # yyuu/pyenv#257
-  stub uname '-s : echo Linux'
-  stub uname '-s : echo Linux'
+  for i in {1..4}; do stub uname '-s : echo Darwin'; done
 
   PYTHON_MAKE_INSTALL_TARGET="altinstall" TMPDIR="$TMP" install_tmp_fixture definitions/vanilla-python < /dev/null
   assert_success
@@ -259,10 +255,7 @@ OUT
   touch "${INSTALL_ROOT}/Library/Frameworks/Python.framework/Versions/Current/bin/python3.4-config"
   chmod +x "${INSTALL_ROOT}/Library/Frameworks/Python.framework/Versions/Current/bin/python3.4-config"
 
-  # yyuu/pyenv#257
-  stub uname '-s : echo Darwin'
-
-  stub uname '-s : echo Darwin'
+  for i in {1..3}; do stub uname '-s : echo Darwin'; done
 
   PYTHON_CONFIGURE_OPTS="--enable-framework" TMPDIR="$TMP" run_inline_definition <<OUT
 echo "PYTHON_CONFIGURE_OPTS_ARRAY=(\${PYTHON_CONFIGURE_OPTS_ARRAY[@]})"
@@ -278,10 +271,8 @@ EOS
 }
 
 @test "enable universalsdk" {
-  # yyuu/pyenv#257
-  stub uname '-s : echo Darwin'
-
-  stub uname '-s : echo Darwin'
+  
+  for i in {1..3}; do stub uname '-s : echo Darwin'; done
 
   PYTHON_CONFIGURE_OPTS="--enable-universalsdk" TMPDIR="$TMP" run_inline_definition <<OUT
 echo "PYTHON_CONFIGURE_OPTS_ARRAY=(\${PYTHON_CONFIGURE_OPTS_ARRAY[@]})"
@@ -295,7 +286,8 @@ EOS
 @test "enable custom unicode configuration" {
   cached_tarball "Python-3.6.2"
 
-  stub brew false
+  for i in {1..2}; do stub brew '* : false'; done
+  for i in {1..3}; do stub uname '-s : echo Linux'; done
   stub "$MAKE" \
     " : echo \"$MAKE \$@\" >> build.log" \
     " : echo \"$MAKE \$@\" >> build.log && cat build.log >> '$INSTALL_ROOT/build.log'"
@@ -311,6 +303,8 @@ make install
 OUT
 
   unstub make
+  unstub uname
+  unstub brew
 }
 
 @test "default MACOSX_DEPLOYMENT_TARGET" {
diff --git a/plugins/python-build/test/stubs/stub b/plugins/python-build/test/stubs/stub
index bd5c5d68..5ff72b81 100755
--- a/plugins/python-build/test/stubs/stub
+++ b/plugins/python-build/test/stubs/stub
@@ -11,11 +11,10 @@ _STUB_RUN="${PROGRAM}_STUB_RUN"
 _STUB_INDEX="${PROGRAM}_STUB_INDEX"
 _STUB_RESULT="${PROGRAM}_STUB_RESULT"
 _STUB_END="${PROGRAM}_STUB_END"
-_STUB_DEBUG="${PROGRAM}_STUB_DEBUG"
+_STUB_LOG="${PROGRAM}_STUB_LOG"
 
-if [ -n "${!_STUB_DEBUG}" ]; then
-  echo "$program" "$@" >&${!_STUB_DEBUG}
-fi
+[ -n "${!_STUB_LOG}" ] || eval "${_STUB_LOG}"="${TMPDIR}/${program}-stub-log"
+if test -z "${!_STUB_END}"; then echo "$program" "$@" >>"${!_STUB_LOG}"; fi
 
 [ -e "${!_STUB_PLAN}" ] || exit 1
 [ -n "${!_STUB_RUN}" ] || eval "${_STUB_RUN}"="${TMPDIR}/${program}-stub-run"
@@ -24,7 +23,7 @@ fi
 # Initialize or load the stub run information.
 eval "${_STUB_INDEX}"=1
 eval "${_STUB_RESULT}"=0
-[ ! -e "${!_STUB_RUN}" ] || source "${!_STUB_RUN}"
+if test -e "${!_STUB_RUN}"; then source "${!_STUB_RUN}"; fi
 
 
 # Loop over each line in the plan.
@@ -80,14 +79,39 @@ done < "${!_STUB_PLAN}"
 
 
 if [ -n "${!_STUB_END}" ]; then
-  # Clean up the run file.
-  rm -f "${!_STUB_RUN}"
-
   # If the number of lines in the plan is larger than
   # the requested index, we failed.
   if [ $index -ge "${!_STUB_INDEX}" ]; then
     eval "${_STUB_RESULT}"=1
+    {
+      echo "index: $index; stub index: ${!_STUB_INDEX}"
+      echo "plan:"
+      cat "${!_STUB_PLAN}"
+      echo "run:"
+      cat "${!_STUB_RUN}"
+      echo "log:"
+      cat "${!_STUB_LOG}"
+    } >&2
   fi
+  if [ "${!_STUB_RESULT}" -ne 0 ]; then
+    {
+      echo "index: $index; stub index: ${!_STUB_INDEX}"
+      echo "plan:"
+      cat "${!_STUB_PLAN}" || true
+      echo "run:"
+      cat "${!_STUB_RUN}" || true
+      echo "log:"
+      cat "${!_STUB_LOG}" || true
+    } >&2
+  fi
+
+  # Clean up the run file.
+  rm -f "${!_STUB_RUN}"
+  rm -f "${!_STUB_LOG}"
+
+  # Clean up the run file.
+  rm -f "${!_STUB_RUN}"
+  rm -f "${!_STUB_LOG}"
 
   # Return the result.
   exit "${!_STUB_RESULT}"
diff --git a/plugins/python-build/test/test_helper.bash b/plugins/python-build/test/test_helper.bash
index c7494f64..da52a44f 100644
--- a/plugins/python-build/test/test_helper.bash
+++ b/plugins/python-build/test/test_helper.bash
@@ -25,6 +25,7 @@ stub() {
 
   export "${prefix}_STUB_PLAN"="${TMP}/${program}-stub-plan"
   export "${prefix}_STUB_RUN"="${TMP}/${program}-stub-run"
+  export "${prefix}_STUB_LOG"="${TMP}/${program}-stub-log"
   export "${prefix}_STUB_END"=
 
   mkdir -p "${TMP}/bin"
diff --git a/plugins/python-build/test/version.bats b/plugins/python-build/test/version.bats
index 370abc74..15c8635f 100644
--- a/plugins/python-build/test/version.bats
+++ b/plugins/python-build/test/version.bats
@@ -32,8 +32,7 @@ static_version="$(grep VERSION "$bats_bin" | head -1 | cut -d'"' -f 2)"
 
 @test "git remote doesn't match" {
   stub git \
-    'remote -v : echo origin https://github.com/Homebrew/homebrew.git' \
-    "describe --tags HEAD : echo v1984-12-gSHA"
+    'remote -v : echo origin https://github.com/Homebrew/homebrew.git'
   run python-build --version
   assert_success "python-build ${static_version}"
 }
diff --git a/test/exec.bats b/test/exec.bats
index 61b4711d..56a0f61e 100644
--- a/test/exec.bats
+++ b/test/exec.bats
@@ -79,7 +79,7 @@ OUT
 }
 
 @test "sys.executable with system version (#98)" {
-  system_python=$(which python3)
+  system_python="$(python3 -c 'import sys; print(sys.executable)')"
 
   PYENV_VERSION="custom"
   create_executable "python3" ""
diff --git a/test/prefix.bats b/test/prefix.bats
index 5da1a5f8..adf27baf 100644
--- a/test/prefix.bats
+++ b/test/prefix.bats
@@ -25,7 +25,7 @@ load test_helper
 }
 
 #Arch has Python at sbin as well as bin
-@test "prefix for sbin system" {
+@test "prefix for system in sbin" {
   mkdir -p "${PYENV_TEST_DIR}/sbin"
   touch "${PYENV_TEST_DIR}/sbin/python"
   chmod +x "${PYENV_TEST_DIR}/sbin/python"
@@ -46,6 +46,6 @@ OUT
 }
 
 @test "prefix for invalid system" {
-  PATH="$(path_without python)" run pyenv-prefix system
+  PATH="$(path_without python python2 python3)" run pyenv-prefix system
   assert_failure "pyenv: system version not found in PATH"
 }
diff --git a/test/test_helper.bash b/test/test_helper.bash
index e11cd8f1..30615cd3 100644
--- a/test/test_helper.bash
+++ b/test/test_helper.bash
@@ -44,7 +44,8 @@ flunk() {
 
 assert_success() {
   if [ "$status" -ne 0 ]; then
-    flunk "command failed with exit status $status"
+    flunk "command failed with exit status $status" $'\n'\
+    "output: $output"
   elif [ "$#" -gt 0 ]; then
     assert_output "$1"
   fi
@@ -52,7 +53,8 @@ assert_success() {
 
 assert_failure() {
   if [ "$status" -eq 0 ]; then
-    flunk "expected failed exit status"
+    flunk "expected failed exit status" $'\n'\
+    "output: $output"
   elif [ "$#" -gt 0 ]; then
     assert_output "$1"
   fi
@@ -111,24 +113,26 @@ assert() {
 # Output a modified PATH that ensures that the given executable is not present,
 # but in which system utils necessary for pyenv operation are still available.
 path_without() {
-  local exe="$1"
   local path=":${PATH}:"
-  local found alt util
-  for found in $(which -a "$exe"); do
-    found="${found%/*}"
-    if [ "$found" != "${PYENV_ROOT}/shims" ]; then
-      alt="${PYENV_TEST_DIR}/$(echo "${found#/}" | tr '/' '-')"
-      mkdir -p "$alt"
-      for util in bash head cut readlink greadlink; do
-        if [ -x "${found}/$util" ]; then
-          ln -s "${found}/$util" "${alt}/$util"
-        fi
-      done
-      path="${path/:${found}:/:${alt}:}"
-    fi
+  for exe; do 
+    local found alt util
+    for found in $(PATH="$path" which -a "$exe"); do
+      found="${found%/*}"
+      if [ "$found" != "${PYENV_ROOT}/shims" ]; then
+        alt="${PYENV_TEST_DIR}/$(echo "${found#/}" | tr '/' '-')"
+        mkdir -p "$alt"
+        for util in bash head cut readlink greadlink which; do
+          if [ -x "${found}/$util" ]; then
+            ln -s "${found}/$util" "${alt}/$util"
+          fi
+        done
+        path="${path/:${found}:/:${alt}:}"
+      fi
+    done
   done
   path="${path#:}"
-  echo "${path%:}"
+  path="${path%:}"
+  echo "$path"
 }
 
 create_hook() {
diff --git a/test/versions.bats b/test/versions.bats
index 8ded5c4a..932883c7 100644
--- a/test/versions.bats
+++ b/test/versions.bats
@@ -25,7 +25,7 @@ stub_system_python() {
 }
 
 @test "not even system python available" {
-  PATH="$(path_without python)" run pyenv-versions
+  PATH="$(path_without python python2 python3)" run pyenv-versions
   assert_failure
   assert_output "Warning: no Python detected on the system"
 }