test(api): cover everyTick helper

api/main_test.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	"context"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// TestEveryTick_CallsFnOnTick verifies the helper invokes fn repeatedly on its
+// interval. A non-blocking send keeps the spawned goroutine from ever blocking
+// on a full channel, and the 1s timeout per tick is generous vs the 1ms
+// interval so the test in not timing-flaky.
+func TestEveryTick_CallsFnOnTick(t *testing.T) {
+	ctx := t.Context()
+
+	fired := make(chan struct{}, 1)
+	everyTick(ctx, time.Millisecond, func(context.Context) {
+		select {
+		case fired <- struct{}{}:
+		default:
+		}
+	})
+
+	for i := range 3 {
+		select {
+		case <-fired:
+		case <-time.After(time.Second):
+			t.Fatalf("tick %d did not fire within 1s", i+1)
+		}
+	}
+}
+
+// TestEveryTick_StopsOnContextCancel verifies cancelling ctx stops the loop.
+// Once cancel propagates the call count must stop growing. This is the property
+// that lets the reconciler goroutines exit on graceful shutdown
+func TestEveryTick_StopsOnContextCancel(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+
+	var calls int64
+	started := make(chan struct{}, 1)
+	everyTick(ctx, time.Millisecond, func(context.Context) {
+		atomic.AddInt64(&calls, 1)
+		select {
+		case started <- struct{}{}:
+		default:
+		}
+	})
+
+	// Wait until the loop is actually running before cancelling.
+	select {
+	case <-started:
+	case <-time.After(time.Second):
+		t.Fatalf("everyTick never called fn")
+	}
+
+	cancel()
+	time.Sleep(20 * time.Millisecond) // let cancel land + any in-flight tick finish
+	stable := atomic.LoadInt64(&calls)
+
+	time.Sleep(30 * time.Millisecond) // 30 more ticks would land if still running
+	if final := atomic.LoadInt64(&calls); final != stable {
+		t.Fatalf("everyTick kept calling fn after cancel: %d -> %d", stable, final)
+	}
+}
+
+func TestEveryTick_PassesContextToFn(t *testing.T) {
+	type ctxKey string
+	const marker ctxKey = "marker"
+	ctx, cancel := context.WithCancel(context.WithValue(context.Background(), marker, "present"))
+	defer cancel()
+
+	got := make(chan string, 1)
+	everyTick(ctx, time.Millisecond, func(c context.Context) {
+		v, _ := c.Value(marker).(string)
+		select {
+		case got <- v:
+		default:
+		}
+	})
+
+	select {
+	case v := <-got:
+		if v != "present" {
+			t.Fatalf("fn received wrong context: value = %q, want %q", v, "present")
+		}
+	case <-time.After(time.Second):
+		t.Fatalf("fn never ran")
+	}
+}