Feature request 241: reuse mocks in MockLink / MockedProvider

.api-reports/api-report-testing.md

@@ -888,6 +888,8 @@ export interface MockedResponse<TData = Record<string, any>, TVariables = Record
     // (undocumented)
     error?: Error;
     // (undocumented)
+    maxUsageCount?: number;
+    // (undocumented)
     newData?: ResultFunction<FetchResult>;
     // (undocumented)
     request: GraphQLRequest<TVariables>;

.api-reports/api-report-testing_core.md

@@ -844,6 +844,8 @@ export interface MockedResponse<TData = Record<string, any>, TVariables = Record
     // (undocumented)
     error?: Error;
     // (undocumented)
+    maxUsageCount?: number;
+    // (undocumented)
     newData?: ResultFunction<FetchResult>;
     // (undocumented)
     request: GraphQLRequest<TVariables>;

.changeset/yellow-flies-repeat.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": minor
+---
+
+Support re-using of mocks in the MockedProvider

.github/workflows/api-extractor.yml

@@ -19,8 +19,6 @@ jobs:
       - name: Install dependencies (with cache)
         uses: bahmutov/npm-install@v1
 
-      - name: Run build
-        run: npm run build
-
+        # Builds the library and runs the api extractor
       - name: Run Api-Extractor
         run: npm run extract-api

.size-limit.cjs

@@ -1,7 +1,7 @@
 const checks = [
   {
     path: "dist/apollo-client.min.cjs",
-    limit: "37986",
+    limit: "38000",
   },
   {
     path: "dist/main.cjs",

docs/source/development-testing/testing.mdx

@@ -150,6 +150,37 @@ it("renders without error", async () => {
 
 </ExpansionPanel>
 
+#### Reusing mocks
+
+By default, a mock is only used once. If you want to reuse a mock for multiple operations, you can set the `maxUsageCount` field to a number indicating how many times the mock should be used:
+
+<ExpansionPanel title="Click to expand 🐶">
+
+```jsx title="dog.test.js"
+import { GET_DOG_QUERY } from "./dog";
+
+const mocks = [
+  {
+    request: {
+      query: GET_DOG_QUERY,
+      variables: {
+        name: "Buck"
+      }
+    },
+    result: {
+      data: {
+        dog: { id: "1", name: "Buck", breed: "bulldog" }
+      }
+    },
+    maxUsageCount: 2, // The mock can be used twice before it's removed, default is 1
+  }
+];
+```
+
+</ExpansionPanel>
+
+Passing `Number.POSITIVE_INFINITY` will cause the mock to be reused indefinitely.
+
 ### Dynamic variables
 
 Sometimes, the exact value of the variables being passed are not known. The `MockedResponse` object takes a `variableMatcher` property that is a function that takes the variables and returns a boolean indication if this mock should match the invocation for the provided query. You cannot specify this parameter and `request.variables` at the same time.

package.json

@@ -42,7 +42,7 @@
     "prepdist": "node ./config/prepareDist.js",
     "prepdist:changesets": "ts-node-script config/prepareChangesetsRelease.ts",
     "postprocess-dist": "ts-node-script config/postprocessDist.ts",
-    "extract-api": "ts-node-script config/apiExtractor.ts",
+    "extract-api": "npm run build && ts-node-script config/apiExtractor.ts",
     "clean": "rimraf dist coverage lib temp",
     "check:format": "prettier --check .",
     "ci:precheck": "node config/precheck.js",

src/testing/core/mocking/mockLink.ts

@@ -30,6 +30,7 @@ export interface MockedResponse<
   TVariables = Record<string, any>,
 > {
   request: GraphQLRequest<TVariables>;
+  maxUsageCount?: number;
   result?: FetchResult<TData> | ResultFunction<FetchResult<TData>, TVariables>;
   error?: Error;
   delay?: number;
@@ -135,8 +136,11 @@ ${unmatchedVars.map((d) => `  ${stringifyForDisplay(d)}`).join("\n")}
         );
       }
     } else {
-      mockedResponses.splice(responseIndex, 1);
-
+      if (response.maxUsageCount! > 1) {
+        response.maxUsageCount!--;
+      } else {
+        mockedResponses.splice(responseIndex, 1);
+      }
       const { newData } = response;
       if (newData) {
         response.result = newData(operation.variables);
@@ -203,6 +207,14 @@ ${unmatchedVars.map((d) => `  ${stringifyForDisplay(d)}`).join("\n")}
     if (query) {
       newMockedResponse.request.query = query;
     }
+
+    mockedResponse.maxUsageCount = mockedResponse.maxUsageCount ?? 1;
+    invariant(
+      mockedResponse.maxUsageCount > 0,
+      `Mock response maxUsageCount must be greater than 0, %s given`,
+      mockedResponse.maxUsageCount
+    );
+
     this.normalizeVariableMatching(newMockedResponse);
     return newMockedResponse;
   }