Add Nil and NotNil assertions

CHANGELOG.md

@@ -19,6 +19,7 @@ The main additions are the new assertions for
 ### Added
 
 - Add `True`, `False`, assertion functions.
+- Add `Nil`, `NotNil`, assertion functions.
 - Add `NoError`, `IsError` assertion functions.
 - Add `Panics`, `NoPanic` assertion functions.
 - Add `Eventually`, `EventuallyChan` assertion functions.

nil.go

@@ -0,0 +1,23 @@
+package verify
+
+import "fmt"
+
+// Nil tests if provided interface value is nil.
+// Use it only for interfaces.
+// For structs and pointers use Obj(got).Zero().
+func Nil(v interface{}) FailureMessage {
+	if v == nil {
+		return ""
+	}
+	return FailureMessage(fmt.Sprintf("value is not nil\ngot: %+v", v))
+}
+
+// NotNil tests if provided interface is not nil.
+// Use it only for interfaces.
+// For structs and pointers use Obj(got).NonZero().
+func NotNil(v any) FailureMessage {
+	if v != nil {
+		return ""
+	}
+	return "value is <nil>"
+}

nil_test.go

@@ -0,0 +1,31 @@
+package verify_test
+
+import (
+	"testing"
+
+	"github.com/fluentassert/verify"
+)
+
+func TestNil(t *testing.T) {
+	t.Run("Passed", func(t *testing.T) {
+		var err error
+		msg := verify.Nil(err)
+		assertPassed(t, msg)
+	})
+	t.Run("Failed", func(t *testing.T) {
+		msg := verify.Nil(0)
+		assertFailed(t, msg, "value is not nil")
+	})
+}
+
+func TestNotNil(t *testing.T) {
+	t.Run("Passed", func(t *testing.T) {
+		msg := verify.NotNil(0)
+		assertPassed(t, msg)
+	})
+	t.Run("Failed", func(t *testing.T) {
+		var err error
+		msg := verify.NotNil(err)
+		assertFailed(t, msg, "value is <nil>")
+	})
+}