Remove null from level enum and add schema validation tests

Co-authored-by: aaronburtle <93220300+aaronburtle@users.noreply.github.com>

Author: Copilot

schemas/dab.draft.schema.json

@@ -813,7 +813,7 @@
                     "level": {
                       "type": "string",
                       "description": "Cache level (L1 or L1L2)",
-                      "enum": [ "L1", "L1L2", null ],
+                      "enum": [ "L1", "L1L2" ],
                       "default": "L1L2"
                     }
                   }
@@ -1137,7 +1137,7 @@
                 "level": {
                   "type": "string",
                   "description": "Cache level (L1 or L1L2)",
-                  "enum": [ "L1", "L1L2", null ],
+                  "enum": [ "L1", "L1L2" ],
                   "default": "L1L2"
                 }
               }

src/Service.Tests/Configuration/ConfigurationTests.cs

@@ -1966,6 +1966,63 @@ public void TestBasicConfigSchemaWithNoEntityFieldsIsInvalid()
             Assert.IsTrue(result.ErrorMessage.Contains("Total schema validation errors: 1\n> Required properties are missing from object: entities."));
         }
 
+        /// <summary>
+        /// Validates that the JSON schema correctly validates entity cache configuration properties.
+        /// Tests both valid configurations (proper level values, ttl >= 1) and invalid configurations
+        /// (invalid level values, ttl = 0).
+        /// </summary>
+        [DataTestMethod]
+        [DataRow("L1", 10, true, DisplayName = "Valid cache config with L1 and ttl=10")]
+        [DataRow("L1L2", 1, true, DisplayName = "Valid cache config with L1L2 and minimum ttl=1")]
+        [DataRow("L1L2", 3600, true, DisplayName = "Valid cache config with L1L2 and ttl=3600")]
+        [DataRow("L3", 10, false, DisplayName = "Invalid cache config with invalid level L3")]
+        [DataRow("L1", 0, false, DisplayName = "Invalid cache config with ttl=0 (below minimum)")]
+        [DataRow("L1L2", -1, false, DisplayName = "Invalid cache config with negative ttl")]
+        public void TestEntityCacheSchemaValidation(string level, int ttlSeconds, bool shouldBeValid)
+        {
+            string jsonData = $@"{{
+                ""$schema"": ""https://github.com/Azure/data-api-builder/releases/download/vmajor.minor.patch/dab.draft.schema.json"",
+                ""data-source"": {{
+                    ""database-type"": ""mssql"",
+                    ""connection-string"": ""Server=test;Database=test;""
+                }},
+                ""entities"": {{
+                    ""Book"": {{
+                        ""source"": {{
+                            ""object"": ""books"",
+                            ""type"": ""table""
+                        }},
+                        ""permissions"": [{{
+                            ""role"": ""anonymous"",
+                            ""actions"": [""read""]
+                        }}],
+                        ""cache"": {{
+                            ""enabled"": true,
+                            ""ttl-seconds"": {ttlSeconds},
+                            ""level"": ""{level}""
+                        }}
+                    }}
+                }}
+            }}";
+
+            Mock<ILogger<JsonConfigSchemaValidator>> schemaValidatorLogger = new();
+            string jsonSchema = File.ReadAllText("dab.draft.schema.json");
+            JsonConfigSchemaValidator jsonSchemaValidator = new(schemaValidatorLogger.Object, new MockFileSystem());
+
+            JsonSchemaValidationResult result = jsonSchemaValidator.ValidateJsonConfigWithSchema(jsonSchema, jsonData);
+
+            if (shouldBeValid)
+            {
+                Assert.IsTrue(result.IsValid, $"Expected valid config but got errors: {result.ErrorMessage}");
+                Assert.IsTrue(EnumerableUtilities.IsNullOrEmpty(result.ValidationErrors));
+            }
+            else
+            {
+                Assert.IsFalse(result.IsValid, "Expected validation to fail but it passed");
+                Assert.IsFalse(EnumerableUtilities.IsNullOrEmpty(result.ValidationErrors));
+            }
+        }
+
         /// <summary>
         /// This test tries to validate a runtime config file that is not compliant with the runtime config JSON schema.
         /// It validates no additional properties are defined in the config file.