feat(cli): include chaos option in Spectra config

packages/cli/src/util/__tests__/config.spec.ts

@@ -0,0 +1,78 @@
+import { assertValidConfig, type Config } from '../config';
+
+describe('assertValidConfig', () => {
+  it('should not throw an error for a valid config', () => {
+    const validConfig: Config = {
+      ignoreExamples: true,
+      dynamic: false,
+      jsonSchemaFakerFillProperties: true,
+      chaos: {
+        enabled: true,
+        rate: 50,
+        codes: [500, 502],
+      },
+    };
+
+    expect(assertValidConfig.bind(null, validConfig)).not.toThrow();
+  });
+
+  it('should throw an error for an invalid config', () => {
+    const invalidConfig = {
+      ignoreExamples: 'true', // invalid type
+      dynamic: false,
+      jsonSchemaFakerFillProperties: true,
+      chaos: {
+        enabled: true,
+        rate: 50,
+        codes: [500, 502],
+      },
+    };
+
+    expect(assertValidConfig.bind(null, invalidConfig)).toThrow();
+  });
+
+  it('should throw an error for a config with missing required properties', () => {
+    const invalidConfig = {
+      dynamic: false,
+      jsonSchemaFakerFillProperties: true,
+      chaos: {
+        enabled: true,
+        rate: 50,
+      },
+    };
+
+    expect(assertValidConfig.bind(null, invalidConfig)).toThrow();
+  });
+
+  it('should throw an error for a config with additional properties', () => {
+    const invalidConfig = {
+      ignoreExamples: true,
+      dynamic: false,
+      jsonSchemaFakerFillProperties: true,
+      extraProperty: 'not allowed',
+    };
+
+    expect(assertValidConfig.bind(null, invalidConfig)).toThrow();
+  });
+
+  it('should throw an error for a config with enabled chaos and no/empty codes', () => {
+    expect(
+      assertValidConfig.bind(null, {
+        chaos: {
+          enabled: true,
+          rate: 50,
+        },
+      })
+    ).toThrow();
+
+    expect(
+      assertValidConfig.bind(null, {
+        chaos: {
+          enabled: true,
+          rate: 50,
+          codes: [],
+        },
+      })
+    ).toThrow();
+  });
+});

packages/cli/src/util/config.ts

@@ -1,10 +1,29 @@
 import { promises as fs } from 'fs';
-import * as Ajv from 'ajv';
+import * as Ajv from 'ajv/dist/2020';
 import type * as pino from 'pino';
 import type { CreateMockServerOptions } from './createServer';
 import type { Observable } from './observable';
 
-const ajv = new Ajv.Ajv({
+export type Config = {
+  ignoreExamples?: boolean;
+  dynamic?: boolean;
+  jsonSchemaFakerFillProperties?: boolean;
+  chaos?: {
+    enabled?: boolean;
+    rate?: number;
+    codes?: number[];
+  } & (
+    | {
+        enabled: true;
+        codes: [number, ...number[]];
+      }
+    | {
+        enabled?: false;
+      }
+  );
+};
+
+const ajv = new Ajv.Ajv2020({
   strict: true,
   allErrors: true,
 });
@@ -15,10 +34,54 @@ const validate = ajv.compile({
     ignoreExamples: { type: 'boolean' },
     dynamic: { type: 'boolean' },
     jsonSchemaFakerFillProperties: { type: 'boolean' },
-  } satisfies Partial<Record<keyof CreateMockServerOptions, unknown>>,
+    chaos: {
+      type: 'object',
+      unevaluatedProperties: false,
+      properties: {
+        enabled: { type: 'boolean' },
+        rate: {
+          type: 'number',
+          minimum: 0,
+          maximum: 100,
+        },
+        codes: {
+          type: 'array',
+          items: {
+            type: 'integer',
+            minimum: 400,
+            exclusiveMaximum: 600,
+          },
+          uniqueItems: true,
+        },
+      },
+      oneOf: [
+        {
+          properties: {
+            enabled: { const: true },
+            codes: {
+              type: 'array',
+              minItems: 1,
+            },
+          },
+          required: ['enabled', 'codes'],
+        },
+        {
+          properties: {
+            enabled: { const: false },
+          },
+        },
+      ],
+    },
+  } satisfies Partial<Record<keyof Config, unknown>>,
   additionalProperties: false,
 });
 
+export function assertValidConfig(input: unknown): asserts input is Config {
+  if (!validate(input)) {
+    throw new Error(ajv.errorsText(validate.errors));
+  }
+}
+
 export async function safeApplyConfig(
   logInstance: pino.Logger,
   defaultConfig: CreateMockServerOptions,

packages/cli/src/util/createServer.ts

@@ -5,9 +5,11 @@ import * as chalk from 'chalk';
 import * as cluster from 'cluster';
 import * as E from 'fp-ts/Either';
 import { pipe } from 'fp-ts/function';
+import * as O from 'fp-ts/Option';
 import * as pino from 'pino';
 import * as signale from 'signale';
 import * as split from 'split2';
+
 import { PassThrough, Readable } from 'stream';
 import { LOG_COLOR_MAP } from '../const/options';
 import { CreatePrism } from './runner';
@@ -94,6 +96,27 @@ async function createPrismServerWithLogger(options: Observable<CreateBaseServerO
     errors: options.errors,
     upstreamProxy: undefined,
     mock: {
+      get chaos(): IHttpConfig['mock']['chaos'] {
+        const rate = options.chaos?.rate ?? 10;
+        return pipe(
+          O.fromNullable(options.chaos),
+          O.fold(
+            () => ({ enabled: false, rate, codes: [] }),
+            chaos =>
+              chaos.enabled === true
+                ? {
+                    enabled: true,
+                    rate,
+                    codes: chaos.codes,
+                  }
+                : {
+                    enabled: false,
+                    rate,
+                    codes: chaos.codes ?? [],
+                  }
+          )
+        );
+      },
       get dynamic() {
         return options.dynamic;
       },
@@ -162,6 +185,19 @@ type CreateBaseServerOptions = {
   config?: string;
   dynamic: boolean;
   cors: boolean;
+  chaos?: {
+    enabled?: boolean;
+    rate?: number;
+    codes?: number[];
+  } & (
+    | {
+        enabled: true;
+        codes: [number, ...number[]];
+      }
+    | {
+        enabled?: false;
+      }
+  );
   host: string;
   port: number;
   document: string;

test-harness/specs/config/chaos.txt

@@ -0,0 +1,50 @@
+====test====
+Given I mock and specify a config with chaos enabled
+When I send a request to an operation
+Then the config should influence the response
+====spec====
+openapi: "3.1.0"
+info:
+  version: "0.0"
+  title: Config Test
+paths:
+  /pets/{petId}:
+    get:
+      description: Get a pet by ID
+      responses:
+        "200":
+          description: A pet
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  name:
+                    const: Odie
+        "401":
+          description: Unauthorized
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  message:
+                    const: Unauthorized
+
+====config====
+{
+  "chaos": {
+    "enabled": true,
+    "rate": 100,
+    "codes": [401]
+  }
+}
+====server====
+mock -p 4010 --config ${config} ${document}
+====command====
+curl -i http://localhost:4010/pets/2
+====expect====
+HTTP/1.1 401 OK
+content-type: application/json
+
+{"message":"Unauthorized"}

test-harness/specs/config/chaos_broken.txt

@@ -0,0 +1,42 @@
+====test====
+Given I mock and specify a broken config
+When I send a request to an operation
+Then the config should not influence the response
+====spec====
+openapi: "3.1.0"
+info:
+  version: "0.0"
+  title: Config Test
+paths:
+  /pets/{petId}:
+    get:
+      description: Get a pet by ID
+      responses:
+        "200":
+          description: A pet
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  name:
+                    type: string
+        "401":
+          description: Unauthorized
+====config====
+{
+    "chaos": {
+      "enabled": true,
+      "rate": 100,
+      "codes": []
+    }
+}
+====server====
+mock -p 4010 --config ${config} ${document}
+====command====
+curl -i http://localhost:4010/pets/2
+====expect====
+HTTP/1.1 200 OK
+content-type: application/json
+
+{"name":"string"}