1 files changed, 57 insertions, 2 deletions

diff --git a/flag_test.go b/flag_test.go
index 0dbe874..aa2f434 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -103,9 +103,14 @@ func TestEverything(t *testing.T) {
 func TestUsage(t *testing.T) {
 	called := false
 	ResetForTesting(func() { called = true })
-	if GetCommandLine().Parse([]string{"--x"}) == nil {
+	err := GetCommandLine().Parse([]string{"--x"})
+	expectedErr := "unknown flag: --x"
+	if err == nil {
 		t.Error("parse did not fail for unknown flag")
 	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
 	if called {
 		t.Error("did call Usage while using ContinueOnError")
 	}
@@ -131,9 +136,14 @@ func TestAddFlagSet(t *testing.T) {
 func TestAnnotation(t *testing.T) {
 	f := NewFlagSet("shorthand", ContinueOnError)
 
-	if err := f.SetAnnotation("missing-flag", "key", nil); err == nil {
+	err := f.SetAnnotation("missing-flag", "key", nil)
+	expectedErr := "no such flag -missing-flag"
+	if err == nil {
 		t.Errorf("Expected error setting annotation on non-existent flag")
 	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
 
 	f.StringP("stringa", "a", "", "string value")
 	if err := f.SetAnnotation("stringa", "key", nil); err != nil {
@@ -349,6 +359,33 @@ func testParse(f *FlagSet, t *testing.T) {
 	} else if f.Args()[0] != extra {
 		t.Errorf("expected argument %q got %q", extra, f.Args()[0])
 	}
+	// Test unknown
+	err := f.Parse([]string{"--unknown"})
+	expectedErr := "unknown flag: --unknown"
+	if err == nil {
+		t.Error("parse did not fail for unknown flag")
+	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
+	// Test invalid
+	err = f.Parse([]string{"--bool=abcdefg"})
+	expectedErr = `invalid argument "abcdefg" for "--bool" flag: strconv.ParseBool: parsing "abcdefg": invalid syntax`
+	if err == nil {
+		t.Error("parse did not fail for invalid argument")
+	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
+	// Test required
+	err = f.Parse([]string{"--int"})
+	expectedErr = `flag needs an argument: --int`
+	if err == nil {
+		t.Error("parse did not fail for missing argument")
+	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
 }
 
 func testParseAll(f *FlagSet, t *testing.T) {
@@ -538,6 +575,24 @@ func TestShorthand(t *testing.T) {
 	if f.ArgsLenAtDash() != 1 {
 		t.Errorf("expected argsLenAtDash %d got %d", f.ArgsLenAtDash(), 1)
 	}
+	// Test unknown
+	err := f.Parse([]string{"-ukn"})
+	expectedErr := "unknown shorthand flag: 'u' in -ukn"
+	if err == nil {
+		t.Error("parse did not fail for unknown shorthand flag")
+	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
+	// Test required
+	err = f.Parse([]string{"-as"})
+	expectedErr = `flag needs an argument: 's' in -s`
+	if err == nil {
+		t.Error("parse did not fail for missing argument")
+	}
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
 }
 
 func TestShorthandLookup(t *testing.T) {