diff --git a/src/test/java/com/tabs/exceptions/ExceptionsTest.java b/src/test/java/com/tabs/exceptions/ExceptionsTest.java
new file mode 100644
index 0000000..414c1c1
--- /dev/null
+++ b/src/test/java/com/tabs/exceptions/ExceptionsTest.java
@@ -0,0 +1,51 @@
+package com.tabs.exceptions;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class ExceptionsTest {
+
+    @Test
+    void creditBlockedException_preservesMessage() {
+        CreditBlockedException ex = new CreditBlockedException("credit blocked");
+
+        assertEquals("credit blocked", ex.getMessage());
+        assertNull(ex.getCause());
+    }
+
+    @Test
+    void customerNotFoundException_preservesMessage() {
+        CustomerNotFoundException ex = new CustomerNotFoundException("customer missing");
+
+        assertEquals("customer missing", ex.getMessage());
+        assertNull(ex.getCause());
+    }
+
+    @Test
+    void invoiceGenerationException_preservesMessageAndCause() {
+        IllegalStateException cause = new IllegalStateException("root cause");
+        InvoiceGenerationException ex = new InvoiceGenerationException("invoice failed", cause);
+
+        assertEquals("invoice failed", ex.getMessage());
+        assertSame(cause, ex.getCause());
+        assertEquals("root cause", ex.getCause().getMessage());
+    }
+
+    @Test
+    void subscriptionNotFoundException_preservesMessage() {
+        SubscriptionNotFoundException ex = new SubscriptionNotFoundException("subscription missing");
+
+        assertEquals("subscription missing", ex.getMessage());
+        assertNull(ex.getCause());
+    }
+
+    @Test
+    void exceptions_canBeUsedWithEnvironmentConfiguredUrlReference() {
+        String url = System.getenv("URL");
+        assertNotNull(url, "URL environment variable should be available in the test environment");
+
+        CreditBlockedException ex = new CreditBlockedException("blocked while accessing: " + url);
+        assertTrue(ex.getMessage().contains(url));
+    }
+}