diff --git a/plugins/python-build/test/pyenv_ext.bats b/plugins/python-build/test/pyenv_ext.bats
new file mode 100644
index 00000000..62232ae5
--- /dev/null
+++ b/plugins/python-build/test/pyenv_ext.bats
@@ -0,0 +1,140 @@
+#!/usr/bin/env bats
+
+load test_helper
+export PYTHON_BUILD_CACHE_PATH="$TMP/cache"
+export MAKE=make
+export MAKE_OPTS="-j 2"
+export CC=cc
+
+export TMP_FIXTURES="$TMP/fixtures"
+
+setup() {
+  mkdir -p "$INSTALL_ROOT"
+  stub md5 false
+  stub curl false
+}
+
+executable() {
+  local file="$1"
+  mkdir -p "${file%/*}"
+  cat > "$file"
+  chmod +x "$file"
+}
+
+cached_tarball() {
+  mkdir -p "$PYTHON_BUILD_CACHE_PATH"
+  pushd "$PYTHON_BUILD_CACHE_PATH" >/dev/null
+  tarball "$@"
+  popd >/dev/null
+}
+
+tarball() {
+  local name="$1"
+  local path="$PWD/$name"
+  local configure="$path/configure"
+  shift 1
+
+  executable "$configure" <<OUT
+#!$BASH
+echo "$name: CPPFLAGS=\\"\$CPPFLAGS\\" LDFLAGS=\\"\$LDFLAGS\\"" >> build.log
+echo "$name: \$@" \${PYTHONOPT:+PYTHONOPT=\$PYTHONOPT} >> build.log
+OUT
+
+  for file; do
+    mkdir -p "$(dirname "${path}/${file}")"
+    touch "${path}/${file}"
+  done
+
+  tar czf "${path}.tar.gz" -C "${path%/*}" "$name"
+}
+
+stub_make_install() {
+  stub "$MAKE" \
+    " : echo \"$MAKE \$@\" >> build.log" \
+    "install : echo \"$MAKE \$@\" >> build.log && cat build.log >> '$INSTALL_ROOT/build.log'"
+}
+
+assert_build_log() {
+  run cat "$INSTALL_ROOT/build.log"
+  assert_output
+}
+
+install_patch() {
+  local name="$1"
+  local patch="$2"
+  [ -n "$patch" ] || patch="python.patch"
+
+  mkdir -p "${TMP_FIXTURES}/${name%/*}/patches/${name##*/}/${patch%/*}"
+  cat > "${TMP_FIXTURES}/${name%/*}/patches/${name##*/}/${patch}"
+}
+
+install_tmp_fixture() {
+  local args
+
+  while [ "${1#-}" != "$1" ]; do
+    args="$args $1"
+    shift 1
+  done
+
+  local name="$1"
+  local destination="$2"
+  [ -n "$destination" ] || destination="$INSTALL_ROOT"
+
+  # Copy fixture to temporary path
+  mkdir -p "${TMP_FIXTURES}/${name%/*}"
+  cp "${FIXTURE_ROOT}/${name}" "${TMP_FIXTURES}/${name}"
+
+  run python-build $args "$TMP_FIXTURES/$name" "$destination"
+}
+
+@test "apply built-in python patch before building" {
+  cached_tarball "Python-3.2.1"
+
+  stub brew false
+  stub_make_install
+  stub patch ' : echo patch "$@" | sed -E "s/\.[[:alnum:]]+$/.XXX/" >> build.log'
+
+  echo | install_patch definitions/vanilla-python "Python-3.2.1/empty.patch"
+
+  TMPDIR="$TMP" install_tmp_fixture definitions/vanilla-python < /dev/null
+  assert_success
+
+  assert_build_log <<OUT
+patch -p0 --force -i $TMP/python-patch.XXX
+Python-3.2.1: CPPFLAGS="-I${TMP}/install/include " LDFLAGS="-L${TMP}/install/lib "
+Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
+make -j 2
+make install
+OUT
+
+  unstub make
+  unstub patch
+}
+
+@test "apply built-in python patches should be sorted by its name" {
+  cached_tarball "Python-3.2.1"
+
+  stub brew false
+  stub_make_install
+  stub patch ' : for arg; do [[ "$arg" == "-"* ]] || sed -e "s/^/patch: /" "$arg"; done >> build.log'
+
+  echo "foo" | install_patch definitions/vanilla-python "Python-3.2.1/foo.patch"
+  echo "bar" | install_patch definitions/vanilla-python "Python-3.2.1/bar.patch"
+  echo "baz" | install_patch definitions/vanilla-python "Python-3.2.1/baz.patch"
+
+  TMPDIR="$TMP" install_tmp_fixture definitions/vanilla-python < /dev/null
+  assert_success
+
+  assert_build_log <<OUT
+patch: bar
+patch: baz
+patch: foo
+Python-3.2.1: CPPFLAGS="-I${TMP}/install/include " LDFLAGS="-L${TMP}/install/lib "
+Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
+make -j 2
+make install
+OUT
+
+  unstub make
+  unstub patch
+}
diff --git a/test/pyenv.bats b/test/pyenv.bats
index 811f3cc5..5710ea62 100644
--- a/test/pyenv.bats
+++ b/test/pyenv.bats
@@ -45,11 +45,3 @@ load test_helper
   assert_failure
   assert_output "pyenv: cannot change working directory to \`$dir'"
 }
-
-@test "conflicting GREP_OPTIONS" {
-  file="${BATS_TMPDIR}/hello"
-  echo "hello" > "$file"
-  GREP_OPTIONS="-F" run pyenv grep "hell." "$file"
-  assert_success
-  assert_output "hello"
-}
diff --git a/test/pyenv_ext.bats b/test/pyenv_ext.bats
new file mode 100644
index 00000000..95baa41e
--- /dev/null
+++ b/test/pyenv_ext.bats
@@ -0,0 +1,11 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "conflicting GREP_OPTIONS" {
+  file="${BATS_TMPDIR}/hello"
+  echo "hello" > "$file"
+  GREP_OPTIONS="-F" run pyenv grep "hell." "$file"
+  assert_success
+  assert_output "hello"
+}