diff --git a/optional_marshaljson_int_test.go b/optional_marshaljson_int_test.go
new file mode 100644
index 0000000..d702770
--- /dev/null
+++ b/optional_marshaljson_int_test.go
@@ -0,0 +1,115 @@
+package opt_test
+
+import (
+	"testing"
+
+	"sourcecode.social/reiver/go-opt"
+)
+
+func TestOptional_MarshalJSON_int(t *testing.T) {
+
+	tests := []struct{
+		Value opt.Optional[int]
+	}{
+		{
+			Value: opt.Something(-65536),
+		},
+		{
+			Value: opt.Something(-65535),
+		},
+
+
+
+		{
+			Value: opt.Something(-256),
+		},
+		{
+			Value: opt.Something(-255),
+		},
+
+
+
+		{
+			Value: opt.Something(-5),
+		},
+		{
+			Value: opt.Something(-4),
+		},
+		{
+			Value: opt.Something(-3),
+		},
+		{
+			Value: opt.Something(-2),
+		},
+		{
+			Value: opt.Something(-1),
+		},
+		{
+			Value: opt.Something(0),
+		},
+		{
+			Value: opt.Something(1),
+		},
+		{
+			Value: opt.Something(2),
+		},
+		{
+			Value: opt.Something(3),
+		},
+		{
+			Value: opt.Something(4),
+		},
+		{
+			Value: opt.Something(5),
+		},
+
+
+
+		{
+			Value: opt.Something(255),
+		},
+		{
+			Value: opt.Something(256),
+		},
+
+
+
+		{
+			Value: opt.Something(65535),
+		},
+		{
+			Value: opt.Something(65536),
+		},
+	}
+
+	for testNumber, test := range tests {
+
+		actualBytes, err := test.Value.MarshalJSON()
+		if nil == err {
+			t.Errorf("For test #%d, expected an error but did not actually get one." , testNumber)
+			t.Logf("ACTUAL BYTES: %q", actualBytes)
+			t.Logf("ERROR: (%T) %s", err, err)
+			t.Logf("VALUE: %#v", test.Value)
+			continue
+		}
+	}
+}
+
+func TestOptional_MarshalJSON_int_fail(t *testing.T) {
+
+	var nothing opt.Optional[int]
+
+	actualBytes, err := nothing.MarshalJSON()
+	if nil == err {
+		t.Error("Expected an error but did not actually get one.")
+		t.Logf("ACTUAL: %q", actualBytes)
+		t.Logf("ERROR: (%T) %s", err, err)
+		return
+	}
+	if nil != actualBytes {
+		t.Error("Expected not bytes but actually get some.")
+		t.Logf("ACTUAL: %q", actualBytes)
+		t.Logf("ERROR: (%T) %s", err, err)
+		return
+	}
+}