test.File: No longer use relative path to testdata (#30)

README.md

@@ -49,9 +49,9 @@ func TestSomething(t *testing.T) {
     // Get $CWD/testdata easily
     test.Data(t) // /Users/you/project/package/testdata
 
-    // Check against contents of a file (relative to $CWD/testdata)
-    // including line ending normalisation
-    test.File(t, "hello\n", "expected.txt")
+    // Check against contents of a file including line ending normalisation
+    file := filepath.Join(test.Data(t), "expected.txt")
+    test.File(t, "hello\n", file)
 
     // Just like the good old reflect.DeepEqual, but with a nicer format
     test.DeepEqual(t, []string{"hello"}, []string{"world"}) // Fails

test.go

@@ -182,7 +182,8 @@ func Data(t testing.TB) string {
 
 // File fails if got does not match the contents of the given file.
 //
-// It takes a string and the name of a file (relative to $CWD/testdata) to compare.
+// It takes a string and the path of a file to compare, use [Data] to obtain
+// the path to the current packages testdata directory.
 //
 // If the contents differ, the test will fail with output equivalent to [Diff].
 //
@@ -192,10 +193,13 @@ func Data(t testing.TB) string {
 //	test.File(t, "hello\n", "expected.txt")
 func File(t testing.TB, got, file string) {
 	t.Helper()
-	file = filepath.Join(Data(t), file)
-	contents, err := os.ReadFile(file)
+	f, err := filepath.Abs(file)
 	if err != nil {
-		t.Fatalf("could not read %s: %v", file, err)
+		t.Fatalf("could not make %s absolute: %v", file, err)
+	}
+	contents, err := os.ReadFile(f)
+	if err != nil {
+		t.Fatalf("could not read %s: %v", f, err)
 	}
 
 	contents = bytes.ReplaceAll(contents, []byte("\r\n"), []byte("\n"))

test_test.go

@@ -104,7 +104,7 @@ func TestPass(t *testing.T) {
 		"DeepEqual string slice": func(tb testing.TB) { test.DeepEqual(tb, []string{"hello"}, []string{"hello"}) },
 		"WantErr true":           func(tb testing.TB) { test.WantErr(tb, errors.New("uh oh"), true) },
 		"WantErr false":          func(tb testing.TB) { test.WantErr(tb, nilErr(), false) },
-		"File":                   func(tb testing.TB) { test.File(tb, "hello\n", "file.txt") },
+		"File":                   func(tb testing.TB) { test.File(tb, "hello\n", filepath.Join(test.Data(t), "file.txt")) },
 	}
 
 	for name, fn := range passFns {
@@ -177,7 +177,7 @@ func TestFail(t *testing.T) {
 		"DeepEqual string slice": func(tb testing.TB) { test.DeepEqual(tb, []string{"hello"}, []string{"world"}) },
 		"WantErr true":           func(tb testing.TB) { test.WantErr(tb, errors.New("uh oh"), false) },
 		"WantErr false":          func(tb testing.TB) { test.WantErr(tb, nilErr(), true) },
-		"File wrong":             func(tb testing.TB) { test.File(tb, "wrong\n", "file.txt") },
+		"File wrong":             func(tb testing.TB) { test.File(tb, "wrong\n", filepath.Join(test.Data(t), "file.txt")) },
 		"File missing":           func(tb testing.TB) { test.File(tb, "wrong\n", "missing.txt") },
 	}