enhancing unittest for missing localization text

#207

v2/goi18n/merge_command_test.go

@@ -11,11 +11,12 @@ import (
 )
 
 type testCase struct {
-	name           string
-	inFiles        map[string][]byte
-	sourceLanguage language.Tag
-	outFiles       map[string][]byte
-	deleteFiles    []string
+	name             string
+	inFiles          map[string][]byte
+	sourceLanguage   language.Tag
+	outFiles         map[string][]byte
+	deleteFiles      []string
+	expectedExitCode int
 }
 
 func expectFile(s string) []byte {
@@ -35,6 +36,15 @@ func TestMerge(t *testing.T) {
 				"active.en-US.toml": []byte("1HelloMessage = \"Hello\"\n"),
 			},
 		},
+		{
+			name:           "single identity, no localization text",
+			sourceLanguage: language.AmericanEnglish,
+			inFiles: map[string][]byte{
+				"one.en-US.toml": []byte("1HelloMessage = \"\"\n"),
+			},
+			outFiles:         map[string][]byte{},
+			expectedExitCode: 1,
+		},
 		{
 			name:           "plural identity",
 			sourceLanguage: language.AmericanEnglish,
@@ -518,8 +528,8 @@ zero = "{{.Count}} unread emails"
 			}
 
 			args := append([]string{"merge", "-sourceLanguage", testCase.sourceLanguage.String(), "-outdir", outdir}, infiles...)
-			if code := testableMain(args); code != 0 {
-				t.Fatalf("expected exit code 0; got %d\n", code)
+			if code := testableMain(args); code != testCase.expectedExitCode {
+				t.Fatalf("expected exit code %d; got %d\n", testCase.expectedExitCode, code)
 			}
 
 			files, err := ioutil.ReadDir(outdir)