add AllKinds to the public API. Use it as a single source of truth.

kinds_test.go

@@ -0,0 +1,71 @@
+package lottery
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestAllKindsReturnsExpectedOrder(t *testing.T) {
+	t.Parallel()
+
+	got := AllKinds()
+	want := []Kind{
+		KindLotto,
+		KindEuroMillions,
+		KindSetForLife,
+		KindThunderball,
+		KindPowerball,
+	}
+
+	if len(got) != len(want) {
+		t.Fatalf("expected %d kinds, got %d", len(want), len(got))
+	}
+
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("kind at index %d: expected %q, got %q", i, want[i], got[i])
+		}
+	}
+}
+
+func TestAllKindsReturnsCopy(t *testing.T) {
+	t.Parallel()
+
+	first := AllKinds()
+	first[0] = "mutated"
+
+	again := AllKinds()
+	if again[0] != KindLotto {
+		t.Fatalf("expected AllKinds to return a defensive copy")
+	}
+}
+
+func TestParseKindAcceptsAllKinds(t *testing.T) {
+	t.Parallel()
+
+	for _, kind := range AllKinds() {
+		parsed, err := ParseKind(string(kind))
+		if err != nil {
+			t.Fatalf("expected no error for %q, got %v", kind, err)
+		}
+		if parsed != kind {
+			t.Fatalf("expected %q, got %q", kind, parsed)
+		}
+	}
+}
+
+func TestParseKindIncludesAllKindsInError(t *testing.T) {
+	t.Parallel()
+
+	_, err := ParseKind("invalid")
+	if err == nil {
+		t.Fatalf("expected an error for invalid kind")
+	}
+
+	message := err.Error()
+	for _, kind := range AllKinds() {
+		if !strings.Contains(message, string(kind)) {
+			t.Fatalf("expected error message to contain kind %q: %s", kind, message)
+		}
+	}
+}