chore(go): add release note extraction tests

cmd/vociferate/main_test.go

@@ -36,6 +36,19 @@ func TestMainPrintUnreleasedWritesPendingNotes(t *testing.T) {
 	}
 }
 
+func TestMainPrintReleaseNotesWritesTaggedSection(t *testing.T) {
+	root := t.TempDir()
+	writeFile(t, filepath.Join(root, "CHANGELOG.md"), "# Changelog\n\n## [Unreleased]\n\n### Added\n\n- Feature.\n\n## [1.1.6] - 2017-12-20\n\n### Fixed\n\n- Historical note.\n")
+
+	stdout, stderr, code := runMain(t, "--print-release-notes", "--version", "1.1.6", "--root", root)
+	if code != 0 {
+		t.Fatalf("expected exit 0, got %d (stderr: %s)", code, stderr)
+	}
+	if stdout != "## [1.1.6] - 2017-12-20\n\n### Fixed\n\n- Historical note.\n" {
+		t.Fatalf("unexpected release notes output: %q", stdout)
+	}
+}
+
 func TestMainUsageExitWhenRequiredFlagsMissing(t *testing.T) {
 	_, stderr, code := runMain(t)
 	if code != 2 {

internal/vociferate/vociferate_test.go

@@ -128,6 +128,19 @@ func (s *PrepareSuite) TestUnreleasedBody_ReturnsErrorWhenUnreleasedSectionMissi
 	require.ErrorContains(s.T(), err, "unreleased section")
 }
 
+func (s *PrepareSuite) TestReleaseNotes_ReturnsReleaseSectionForVersion() {
+	notes, err := vociferate.ReleaseNotes(s.rootDir, "1.1.6", vociferate.Options{})
+
+	require.NoError(s.T(), err)
+	require.Equal(s.T(), "## [1.1.6] - 2017-12-20\n\n### Fixed\n\n- Historical note.\n", notes)
+}
+
+func (s *PrepareSuite) TestReleaseNotes_ReturnsErrorWhenVersionSectionMissing() {
+	_, err := vociferate.ReleaseNotes(s.rootDir, "9.9.9", vociferate.Options{})
+
+	require.ErrorContains(s.T(), err, "release notes section")
+}
+
 func (s *PrepareSuite) TestRecommendedTag_ReturnsErrorWhenUnreleasedHasOnlyTemplateHeadings() {
 	require.NoError(s.T(), os.WriteFile(
 		filepath.Join(s.rootDir, "CHANGELOG.md"),