catch innermost spec context timeout

In order to prevent the panic() that occurs if a context timeout
cancel() function fires in the Go testing tool, we execute each test
spec in its own goroutine and catch the individual cancel() function
firing in order to properly output a failed assertion instead of a
panic.

Issue #37

Signed-off-by: Jay Pipes <[email protected]>

scenario/run.go

@@ -93,7 +93,19 @@ func (s *Scenario) Run(ctx context.Context, t *testing.T) error {
 				defer cancel()
 			}
 
-			res, rterr := s.runSpec(specCtx, rt, to, idx, spec)
+			var res *api.Result
+			ch := make(chan runSpecRes, 1)
+
+			go s.runSpec(specCtx, ch, rt, to, idx, spec)
+
+			select {
+			case <-specCtx.Done():
+				t.Fatalf("assertion failed: timeout exceeded (%s)", to.After)
+				break
+			case runres := <-ch:
+				res = runres.r
+				rterr = runres.err
+			}
 			if rterr != nil {
 				break
 			}
@@ -115,14 +127,20 @@ func (s *Scenario) Run(ctx context.Context, t *testing.T) error {
 	return rterr
 }
 
+type runSpecRes struct {
+	r   *api.Result
+	err error
+}
+
 // runSpec executes an individual test spec
 func (s *Scenario) runSpec(
 	ctx context.Context,
+	ch chan runSpecRes,
 	retry *api.Retry,
 	timeout *api.Timeout,
 	idx int,
 	spec api.Evaluable,
-) (*api.Result, error) {
+) {
 	sb := spec.Base()
 	specTraceMsg := strconv.Itoa(idx)
 	if sb.Name != "" {
@@ -136,13 +154,15 @@ func (s *Scenario) runSpec(
 		// Just evaluate the test spec once
 		res, err := spec.Eval(ctx)
 		if err != nil {
-			return nil, err
+			ch <- runSpecRes{nil, err}
+			return
 		}
 		debug.Println(
 			ctx, "run: single-shot (no retries) ok: %v",
 			!res.Failed(),
 		)
-		return res, nil
+		ch <- runSpecRes{res, nil}
+		return
 	}
 
 	// retry the action and test the assertions until they succeed,
@@ -187,7 +207,8 @@ func (s *Scenario) runSpec(
 
 		res, err = spec.Eval(ctx)
 		if err != nil {
-			return nil, err
+			ch <- runSpecRes{nil, err}
+			return
 		}
 		success = !res.Failed()
 		debug.Println(
@@ -206,7 +227,7 @@ func (s *Scenario) runSpec(
 		}
 		attempts++
 	}
-	return res, nil
+	ch <- runSpecRes{res, nil}
 }
 
 // getTimeout returns the timeout configuration for the test spec. We check for