diff --git a/src/test/c/test_calculator.c b/src/test/c/test_calculator.c
index 45970d5..0ab10cf 100644
--- a/src/test/c/test_calculator.c
+++ b/src/test/c/test_calculator.c
@@ -239,4 +239,14 @@ void test_multiplicationbin(void) {
     // Assert
     TEST_ASSERT_EQUAL_INT64(10, result);
 }
+void test_subtractionbin(void) {
+    // Arrange
+    long long int result;
+
+    // Act
+    result = subtractionbin(100,10);
+
+    // Assert
+    TEST_ASSERT_EQUAL_INT64(10, result);
+}