diff --git a/context_test.go b/context_test.go
new file mode 100644
index 0000000..176d013
--- /dev/null
+++ b/context_test.go
@@ -0,0 +1,99 @@
+package clock
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+// Ensure that WithDeadline is cancelled when deadline exceeded.
+func TestMock_WithDeadline(t *testing.T) {
+	m := NewMock()
+	ctx, _ := m.WithDeadline(context.Background(), m.Now().Add(time.Second))
+	m.Add(time.Second)
+	select {
+	case <-ctx.Done():
+		if !errors.Is(ctx.Err(), context.DeadlineExceeded) {
+			t.Error("invalid type of error returned when deadline exceeded")
+		}
+	default:
+		t.Error("context is not cancelled when deadline exceeded")
+	}
+}
+
+// Ensure that WithDeadline does nothing when the deadline is later than the current deadline.
+func TestMock_WithDeadlineLaterThanCurrent(t *testing.T) {
+	m := NewMock()
+	ctx, _ := m.WithDeadline(context.Background(), m.Now().Add(time.Second))
+	ctx, _ = m.WithDeadline(ctx, m.Now().Add(10*time.Second))
+	m.Add(time.Second)
+	select {
+	case <-ctx.Done():
+		if !errors.Is(ctx.Err(), context.DeadlineExceeded) {
+			t.Error("invalid type of error returned when deadline exceeded")
+		}
+	default:
+		t.Error("context is not cancelled when deadline exceeded")
+	}
+}
+
+// Ensure that WithDeadline cancel closes Done channel with context.Canceled error.
+func TestMock_WithDeadlineCancel(t *testing.T) {
+	m := NewMock()
+	ctx, cancel := m.WithDeadline(context.Background(), m.Now().Add(time.Second))
+	cancel()
+	select {
+	case <-ctx.Done():
+		if !errors.Is(ctx.Err(), context.Canceled) {
+			t.Error("invalid type of error returned after cancellation")
+		}
+	case <-time.After(time.Second):
+		t.Error("context is not cancelled after cancel was called")
+	}
+}
+
+// Ensure that WithDeadline closes child contexts after it was closed.
+func TestMock_WithDeadlineCancelledWithParent(t *testing.T) {
+	m := NewMock()
+	parent, cancel := context.WithCancel(context.Background())
+	ctx, _ := m.WithDeadline(parent, m.Now().Add(time.Second))
+	cancel()
+	select {
+	case <-ctx.Done():
+		if !errors.Is(ctx.Err(), context.Canceled) {
+			t.Error("invalid type of error returned after cancellation")
+		}
+	case <-time.After(time.Second):
+		t.Error("context is not cancelled when parent context is cancelled")
+	}
+}
+
+// Ensure that WithDeadline cancelled immediately when deadline has already passed.
+func TestMock_WithDeadlineImmediate(t *testing.T) {
+	m := NewMock()
+	ctx, _ := m.WithDeadline(context.Background(), m.Now().Add(-time.Second))
+	select {
+	case <-ctx.Done():
+		if !errors.Is(ctx.Err(), context.DeadlineExceeded) {
+			t.Error("invalid type of error returned when deadline has already passed")
+		}
+	default:
+		t.Error("context is not cancelled when deadline has already passed")
+	}
+}
+
+// Ensure that WithTimeout is cancelled when deadline exceeded.
+func TestMock_WithTimeout(t *testing.T) {
+	m := NewMock()
+	ctx, _ := m.WithTimeout(context.Background(), time.Second)
+	m.Add(time.Second)
+	select {
+	case <-ctx.Done():
+		if !errors.Is(ctx.Err(), context.DeadlineExceeded) {
+			t.Error("invalid type of error returned when time is over")
+		}
+	default:
+		t.Error("context is not cancelled when time is over")
+	}
+}