Add API contract integration tests for policy management

src/test/java/com/yashdotdev/distributed_traffic_control/policy/api/PolicyControllerIntegrationTest.java

@@ -6,9 +6,12 @@
 import org.springframework.boot.resttestclient.autoconfigure.AutoConfigureTestRestTemplate;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.web.server.LocalServerPort;
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.*;
+import org.springframework.web.util.UriComponentsBuilder;
 
 import java.time.Instant;
+import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -109,4 +112,154 @@ void shouldRejectInvalidPolicyThroughRealHttpEndpoint() throws Exception {
         ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.POST, request, String.class);
         assertEquals(HttpStatus.BAD_REQUEST, response.getStatusCode());
     }
+
+    @Test
+    void shouldListPoliciesThroughRealHttpEndpoint() {
+        String resource = "/api/contract/list";
+
+        restTemplate.exchange(
+                baseUrl(),
+                HttpMethod.POST,
+                createRequest("list-policy", "List Policy", resource, 10),
+                PolicyResponse.class
+        );
+
+        ResponseEntity<List<PolicyResponse>> response =
+                restTemplate.exchange(
+                        baseUrl(),
+                        HttpMethod.GET,
+                        null,
+                        new ParameterizedTypeReference<>() {}
+                );
+
+        assertEquals(HttpStatus.OK, response.getStatusCode());
+        assertNotNull(response.getBody());
+        assertTrue(response.getBody().stream()
+                .anyMatch(policy -> resource.equals(policy.getResource())));
+    }
+
+    @Test
+    void shouldRetrievePolicyByResourceThroughRealHttpEndpoint() {
+        String resource = "/api/contract/read";
+
+        restTemplate.exchange(
+                baseUrl(),
+                HttpMethod.POST,
+                createRequest("read-policy", "Read Policy", resource, 20),
+                PolicyResponse.class
+        );
+
+        ResponseEntity<PolicyResponse> response =
+                restTemplate.getForEntity(
+                        policyUri(resource),
+                        PolicyResponse.class
+                );
+
+        assertEquals(HttpStatus.OK, response.getStatusCode());
+        assertNotNull(response.getBody());
+        assertEquals("read-policy", response.getBody().getPolicyId());
+        assertEquals(resource, response.getBody().getResource());
+        assertEquals(20, response.getBody().getCapacity());
+    }
+
+    @Test
+    void shouldReturnNotFoundForMissingPolicy() {
+        ResponseEntity<String> response =
+                restTemplate.getForEntity(
+                        policyUri("/api/contract/missing"),
+                        String.class
+                );
+
+        assertEquals(HttpStatus.NOT_FOUND, response.getStatusCode());
+    }
+
+    @Test
+    void shouldUpdatePolicyThroughRealHttpEndpoint() {
+        String resource = "/api/contract/update";
+
+        restTemplate.exchange(
+                baseUrl(),
+                HttpMethod.POST,
+                createRequest("update-policy", "Original Policy", resource, 10),
+                PolicyResponse.class
+        );
+
+        ResponseEntity<PolicyResponse> response =
+                restTemplate.exchange(
+                        policyUri(resource),
+                        HttpMethod.PUT,
+                        createRequest("update-policy", "Updated Policy", resource, 50),
+                        PolicyResponse.class
+                );
+
+        assertEquals(HttpStatus.OK, response.getStatusCode());
+        assertNotNull(response.getBody());
+        assertEquals("Updated Policy", response.getBody().getName());
+        assertEquals(50, response.getBody().getCapacity());
+        assertEquals(resource, response.getBody().getResource());
+    }
+
+    @Test
+    void shouldReturnNotFoundAfterDeletingPolicy() {
+        String resource = "/api/contract/delete";
+
+        restTemplate.exchange(
+                baseUrl(),
+                HttpMethod.POST,
+                createRequest("delete-policy-contract", "Delete Policy", resource, 10),
+                PolicyResponse.class
+        );
+
+        ResponseEntity<Void> deleteResponse =
+                restTemplate.exchange(
+                        policyUri(resource),
+                        HttpMethod.DELETE,
+                        HttpEntity.EMPTY,
+                        Void.class
+                );
+
+        assertEquals(HttpStatus.NO_CONTENT, deleteResponse.getStatusCode());
+
+        ResponseEntity<String> getResponse =
+                restTemplate.getForEntity(
+                        policyUri(resource),
+                        String.class
+                );
+
+        assertEquals(HttpStatus.NOT_FOUND, getResponse.getStatusCode());
+    }
+
+    private String baseUrl() {
+        return "http://localhost:" + port + "/api/v1/policies";
+    }
+
+    private java.net.URI policyUri(String resource) {
+        return UriComponentsBuilder.fromUriString(baseUrl())
+                .queryParam("resource", resource)
+                .build()
+                .encode()
+                .toUri();
+    }
+
+    private HttpEntity<String> createRequest(String policyId, String name, String resource, long capacity) {
+
+        HttpHeaders headers = new HttpHeaders();
+        headers.setContentType(MediaType.APPLICATION_JSON);
+
+        String body = """
+                {
+                  "policyId": "%s",
+                  "name": "%s",
+                  "type": "TOKEN_BUCKET",
+                  "status": "ACTIVE",
+                  "capacity": %d,
+                  "refillRate": 1,
+                  "windowDuration": null,
+                  "createdAt": "2026-09-04T00:00:00Z",
+                  "resource": "%s"
+                }
+                """.formatted(policyId, name, capacity, resource);
+
+        return new HttpEntity<>(body, headers);
+    }
 }