testing.md

🧪 Testing Helpers

The package ships assertion helpers that fail a test and print a readable diff, making comparator a drop-in equality checker for your test suite.

✅ AssertEqual / AssertNotEqual

func TestUser(t *testing.T) {
    got := buildUser()
    want := User{Name: "Alice", Role: "admin"}

    comparator.AssertEqual(t, want, got, comparator.IgnoreStructFields("ID", "CreatedAt"))
}

On failure the test is marked failed (via t.Errorf) with a message like:

values are not equal:
Found 1 difference(s)
  .Role: user != admin

• AssertEqual(t, want, got, opts...) — fail unless the values are equal. Returns true when equal.
• AssertNotEqual(t, want, got, opts...) — fail if the values are equal.
• RequireEqual(t, want, got, opts...) — like AssertEqual but stops the test immediately (uses t.Fatalf when available).

All accept the same functional options as the rest of the package, so you can ignore fields, relax float precision, or ignore slice order in assertions.

🧷 The TestingT interface

The helpers accept a small interface rather than *testing.T directly, so the package does not import testing into production builds:

type TestingT interface {
    Helper()
    Errorf(format string, args ...any)
}

*testing.T and *testing.B satisfy it. RequireEqual additionally uses Fatalf when the supplied value implements it.

➡️ Next Steps

• Extend output and behavior: Extensibility.
• Common questions: FAQ.