testscript: expose current subtest in Env (#95)

testscript/testscript.go

@@ -69,6 +69,18 @@ func (e *Env) Defer(f func()) {
 	e.ts.Defer(f)
 }
 
+// T returns the t argument passed to the current test by the T.Run method.
+// Note that if the tests were started by calling Run,
+// the returned value will implement testing.TB.
+// Note that, despite that, the underlying value will not be of type
+// *testing.T because *testing.T does not implement T.
+//
+// If Cleanup is called on the returned value, the function will run
+// after any functions passed to Env.Defer.
+func (e *Env) T() T {
+	return e.ts.t
+}
+
 // Params holds parameters for a call to Run.
 type Params struct {
 	// Dir holds the name of the directory holding the scripts.

testscript/testscript_test.go

@@ -113,6 +113,12 @@ func TestScripts(t *testing.T) {
 				if ts.Value("somekey") != 1234 {
 					ts.Fatalf("test-values did not see expected value")
 				}
+				if ts.Value("t").(T) != ts.t {
+					ts.Fatalf("test-values did not see expected t")
+				}
+				if _, ok := ts.Value("t").(testing.TB); !ok {
+					ts.Fatalf("test-values t does not implement testing.TB")
+				}
 			},
 			"testreadfile": func(ts *TestScript, neg bool, args []string) {
 				if len(args) != 1 {
@@ -165,6 +171,7 @@ func TestScripts(t *testing.T) {
 			}
 			env.Values["setupFilenames"] = setupFilenames
 			env.Values["somekey"] = 1234
+			env.Values["t"] = env.T()
 			env.Vars = append(env.Vars,
 				"GONOSUMDB=*",
 			)