test(reversal): add round-trip validation tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

reversal/roundtrip_test.go

@@ -0,0 +1,93 @@
+package reversal
+
+import (
+	"testing"
+
+	i18n "forge.lthn.ai/core/go-i18n"
+)
+
+// TestRoundTrip_ForwardThenReverse — go-i18n composed output → reversal → verify correct tokens
+func TestRoundTrip_ForwardThenReverse(t *testing.T) {
+	svc, _ := i18n.New()
+	i18n.SetDefault(svc)
+	tok := NewTokeniser()
+
+	tests := []struct {
+		name      string
+		text      string
+		wantVerb  string
+		wantTense string
+	}{
+		{
+			name:      "Progress pattern",
+			text:      i18n.Progress("build"),
+			wantVerb:  "build",
+			wantTense: "gerund",
+		},
+		{
+			name:      "ActionResult pattern",
+			text:      i18n.ActionResult("delete", "file"),
+			wantVerb:  "delete",
+			wantTense: "past",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tokens := tok.Tokenise(tt.text)
+			foundVerb := false
+			for _, tok := range tokens {
+				if tok.Type == TokenVerb && tok.VerbInfo.Base == tt.wantVerb {
+					foundVerb = true
+					if tok.VerbInfo.Tense != tt.wantTense {
+						t.Errorf("verb %q tense = %q, want %q", tt.wantVerb, tok.VerbInfo.Tense, tt.wantTense)
+					}
+				}
+			}
+			if !foundVerb {
+				t.Errorf("did not find verb %q in tokens from %q", tt.wantVerb, tt.text)
+			}
+		})
+	}
+}
+
+// TestRoundTrip_MultiplierImprints — variants should be similar to original
+func TestRoundTrip_MultiplierImprints(t *testing.T) {
+	svc, _ := i18n.New()
+	i18n.SetDefault(svc)
+	tok := NewTokeniser()
+	m := NewMultiplier()
+
+	original := "Delete the configuration file"
+	variants := m.Expand(original)
+	origImprint := NewImprint(tok.Tokenise(original))
+
+	for _, v := range variants {
+		if v == original {
+			continue
+		}
+		varImprint := NewImprint(tok.Tokenise(v))
+		sim := origImprint.Similar(varImprint)
+		if sim < 0.2 {
+			t.Errorf("Variant %q similarity to original = %f, want >= 0.2", v, sim)
+		}
+	}
+}
+
+// TestRoundTrip_SimilarDocuments — similar docs → higher similarity than different docs
+func TestRoundTrip_SimilarDocuments(t *testing.T) {
+	svc, _ := i18n.New()
+	i18n.SetDefault(svc)
+	tok := NewTokeniser()
+
+	imp1 := NewImprint(tok.Tokenise("Delete the configuration file"))
+	imp2 := NewImprint(tok.Tokenise("Delete the old file"))
+	imp3 := NewImprint(tok.Tokenise("Building the project successfully"))
+
+	simSame := imp1.Similar(imp2)
+	simDiff := imp1.Similar(imp3)
+
+	if simSame <= simDiff {
+		t.Errorf("Similar documents (%f) should score higher than different (%f)", simSame, simDiff)
+	}
+}