Add failure test for loan eligibility

tests/test_checkLoanEligibility.c

@@ -32,5 +32,26 @@ void test_checkLoanEligibilitySuccess(void) {
     }
 }
 
+void test_checkLoanEligibilityFailure(void) {
+
+    /* Arrange */
+
+   int user_id[3]   = {12314, 127, 166}; // Random wrong user_ids
+
+   bool result[3];
+
+   /* Act */
+   
+   for (int i = 0; i < 3; i++) {
+        result[i] = checkLoanEligibility(user_id[i]);
+    }   
+
+    /* Assert */
+    
+    for (int i = 0; i < 3; i++) {
+        TEST_ASSERT_FALSE(result[i]);     // Pass if the returned result is false
+    }
+}
+
 
 #endif // TEST