Refine function assertions

CHANGELOG.md

@@ -19,6 +19,8 @@ The main additions are the new assertions for
 ### Added
 
 - Add `True`, `False`, `NoError` assertion functions.
+- Add `Panics`, `NoPanic` assertion functions.
+- Add `Eventually`, `EventuallyChan` assertion functions.
 - Add `Ordered` function which provides following assertions,
   in addition to `Comparable`, via `FluentOrdered` type:
   - `Lesser`

README.md

@@ -122,7 +122,7 @@ $ go test
 TODO
 ```
 
-### Asynchronous (periodic polling)
+### Periodic polling
 
 ```go
 package test
@@ -135,26 +135,23 @@ import (
 	"github.com/fluentassert/verify"
 )
 
-func TestAsync(t *testing.T) {
-	verify.Periodic(10*time.Second, time.Second, func() verify.FailureMessage {
+func TestPeriodic(t *testing.T) {
+	verify.Eventually(10*time.Second, time.Second, func() verify.FailureMessage {
 		client := http.Client{Timeout: time.Second}
 		resp, err := client.Get("http://not-existing:1234")
 		if err != nil {
 			return verify.NoError(err)
 		}
 		return verify.Number(resp.StatusCode).Lesser(300)
-	}).Eventually().Assert(t)
+	}).Assert(t)
 }
 ```
 
 ```sh
 $ go test
---- FAIL: TestAsync (10.00s)
+--- FAIL: TestPeriodic (10.00s)
     async_test.go:19:
-        timeout
-        function always failed
-        last failure message:
-        non-nil error:
+        function never passed, last failure message:
         Get "http://not-existing:1234": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
 ```
 

eventually.go

@@ -0,0 +1,49 @@
+package verify
+
+import (
+	"time"
+)
+
+// Eventually executes the test function until it returns an empty FailureMessage
+// or timeout elapses.
+func Eventually(timeout, interval time.Duration, fn func() FailureMessage) FailureMessage {
+	timer := time.NewTimer(timeout)
+	defer timer.Stop()
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+	return EventuallyChan(timer.C, ticker.C, fn)
+}
+
+// EventuallyChan executes the test function until it returns an empty FailureMessage or timeout elapses.
+func EventuallyChan[TTimerPayload, TTickPayload any](timeout <-chan (TTimerPayload), ticker <-chan (TTickPayload), fn func() FailureMessage) FailureMessage {
+	var err string
+	failMsg := func(cause string) FailureMessage {
+		return FailureMessage("function never passed, last failure message:\n" + err)
+	}
+
+	for {
+		select {
+		case <-timeout:
+			return failMsg("timeout")
+		default:
+		}
+
+		err = string(fn())
+
+		select {
+		case <-timeout:
+			return failMsg("timeout")
+		default:
+		}
+
+		if err == "" {
+			return ""
+		}
+
+		select {
+		case <-timeout:
+			return failMsg("timeout")
+		case <-ticker:
+		}
+	}
+}