errdiff

Overview ¶

Package errdiff makes it easy to compare Error by code, substring or exact match in tests.

Similar in intended usage to messagediff.Diff and pretty.Compare, particularly in table-driven tests.

Example usage:

testCases := []struct {
	...
	wantSubstring string
}{
	// Success
	{...},
	// Failures
	{..., wantSubstring: "failed"},
	{..., wantSubstring: "too many users"},
}
for _, c := range testCases {
	got, err := fn(...)
	if diff := errdiff.Substring(err, c.wantSubstring); diff != "" {
		t.Errorf("fn() %v", diff)
		continue
	}
	...
}

The generic function Check may be used in place of Code or Substring or when comparing against another error or for simple existance of an error:

testCases := []struct {
	...
	err interface{}
}{
	// Success
	{...},
	// Failures
	{..., err: io.EOF},  // An explicit error
	{..., err: "my expected error string"},  // contains text
	{..., err: true}, // expect an error, don't care what
}
for _, c := range testCases {
	got, err := fn(...)
	if diff := errdiff.Check(err, c.err); diff != "" {
		t.Errorf("fn() %v", diff)
		continue
	}
	...