diff --git a/nullable_filter_test.go b/nullable_filter_test.go
new file mode 100644
index 0000000..8af3712
--- /dev/null
+++ b/nullable_filter_test.go
@@ -0,0 +1,61 @@
+package nul_test
+
+import (
+	"testing"
+
+	"sourcecode.social/reiver/go-nul"
+)
+
+func TestOptional_Filter_int(t *testing.T) {
+
+	tests := []struct{
+		Nullable nul.Nullable[int]
+		Expected nul.Nullable[int]
+	}{
+		{
+			Nullable: nul.Nothing[int](),
+			Expected: nul.Nothing[int](),
+		},
+
+
+
+		{
+			Nullable: nul.Something[int](-2),
+			Expected: nul.Something[int](-2),
+		},
+		{
+			Nullable: nul.Something[int](-1),
+			Expected: nul.Nothing[int](),
+		},
+		{
+			Nullable: nul.Something[int](0),
+			Expected: nul.Something[int](0),
+		},
+		{
+			Nullable: nul.Something[int](1),
+			Expected: nul.Nothing[int](),
+		},
+		{
+			Nullable: nul.Something[int](2),
+			Expected: nul.Something[int](2),
+		},
+	}
+
+	for testNumber, test := range tests {
+
+		fn := func(value int) bool {
+			return 0 == (value % 2)
+		}
+
+		actual   := test.Nullable.Filter(fn)
+		expected := test.Expected
+
+		if expected != actual {
+			t.Errorf("For test #%d, the actual value is not what was expected.", testNumber)
+			t.Logf("EXPECTED: %#v", expected)
+			t.Logf("ACTUAL:   %#v", actual)
+	/////////////// CONTINUE
+			continue
+		}
+	}
+}