feat(AppSync): Add JS resolver helper & matchers

doc/matchers/appsync.md

@@ -1,54 +1,43 @@
 # AppSync
 
-A collection of matchers to test mapping templates.
+A collection of matchers to test AWS AppSync mapping templates and JS resolvers.
 
-Use the `appSyncMappingTemplate` helper function with mapping template matchers.
+## Helper Functions
 
-- `template`: A string representing the mapping template
+### `appSyncResolver(input: AppSyncResolverInput)`
+
+Use the `appSyncResolver` helper function to test JS resolvers.
+
+- `code`: The path to a file containing an `APPSYNC_JS` resolver code. The path can either be absolute, or relative to the working directory (`process.cwd()`).
+- `function`: The function to test. Must be `request` or `response`.
+- `context`: The [context object](https://docs.aws.amazon.com/appsync/latest/devguide/resolver-context-reference-js.html) to be passed to the function
+
+### `appSyncMappingTemplate(input: AppSyncMappingTemplateInput)`
+
+Use the `appSyncMappingTemplate` helper function to test VTL mapping templates.
+
+- `template`: The path to a file containing a mapping template. The path can either be absolute, or relative to the working directory (`process.cwd()`).
 - `context`: The [context object](https://docs.aws.amazon.com/appsync/latest/devguide/resolver-context-reference.html#accessing-the-context) to be injected into the template
 
-### `toEvaluateTo<E>(expected: E)`
+## Matchers
 
-Asserts that a mapping template evaluates to a given string or object for a given context.
+### `toEvaluateTo<E>(expected: E)`
 
-If you pass an object as `value`, the matcher will try to parse the generated template into a javascript object before comparing the values.
+Asserts that a mapping template or resolver evaluates to a given object for a given context.
 
 ```typescript
 // matching as a string
 await expect(
-  appSyncMappingTemplate({
-    template: fs.readFileSync('tempalte.vtl', { encoding: 'utf8' }),
+  appSyncResolver({
+    code: __dirname + '/resolver.js',
+    function: 'request',
     context: {
       arguments: {
         id: '123',
       },
     },
   }),
-).toEvaluateTo(`
-{
-  "version" : "2017-02-28",
-  "operation" : "GetItem",
-  "key" : {
-      "pk" : {"S":"123"}
-  }
-}
-`);
-```
-
-```typescript
-// matching as an object also works as long as the mapping template evaluates to a valid JSON
-// otherwise, an error will be thrown
-await expect(
-  appSyncMappingTemplate({
-    template: fs.readFileSync('tempalte.vtl', { encoding: 'utf8' }),
-    context: {
-      arguments: {
-        id: '123',
-      },
-    },
-  }),
-).toEvaluateTo<DynamoDBGetItem>({
-  version: '2017-02-28',
+).toEvaluateTo<DynamoDBGetItemRequest>({
   operation: 'GetItem',
   key: {
     pk: { S: '123' },
@@ -88,12 +77,14 @@ await expect(
     },
   }),
 ).toEvaluateToInlineSnapshot(`
-  {
-    "version" : "2017-02-28",
-    "operation" : "GetItem",
-    "key" : {
-        "pk" : {"S":"123"}
-    }
+  Object {
+    "key": Object {
+      "pk": Object {
+        "S": "789",
+      },
+    },
+    "operation": "GetItem",
+    "version": "2017-02-28",
   }
 `);
 ```

examples/__tests__/__snapshots__/appSync.test.ts.snap

@@ -1,6 +1,17 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`Mapping Template should evaluate a template snapshot as object 1`] = `
+exports[`JS resolvers should evaluate a js resolver with snapshot 1`] = `
+Object {
+  "key": Object {
+    "id": Object {
+      "S": "123",
+    },
+  },
+  "operation": "GetItem",
+}
+`;
+
+exports[`Mapping Template should evaluate a template snapshot 1`] = `
 Object {
   "key": Object {
     "pk": Object {
@@ -11,5 +22,3 @@ Object {
   "version": "2017-02-28",
 }
 `;
-
-exports[`Mapping Template should evaluate a template snapshot as string 1`] = `"hello 456"`;

examples/__tests__/appSync.test.ts

@@ -1,4 +1,5 @@
-import { appSyncMappingTemplate } from 'sls-jest';
+import { DynamoDBGetItemRequest } from '@aws-appsync/utils';
+import { appSyncMappingTemplate, appSyncResolver } from 'sls-jest';
 
 type DynamoDBGetItem = {
   version: string;
@@ -8,44 +9,10 @@ type DynamoDBGetItem = {
   };
 };
 
-const template = `
-#set($id=$ctx.args.id)
-{
-  "version" : "2017-02-28",
-  "operation" : "GetItem",
-  "key" : {
-      "pk" : $util.dynamodb.toDynamoDBJson($id)
-  }
-}
-`;
+const template = __dirname + '/assets/mapping-template.vtl';
 
 describe('Mapping Template', () => {
-  it('should evaluate a template string', async () => {
-    const expected = `
-{
-  "version" : "2017-02-28",
-  "operation" : "GetItem",
-  "key" : {
-      "pk" : {"S":"123"}
-  }
-}
-`;
-
-    // test that the template evaluates to the expected value as a string
-    await expect(
-      appSyncMappingTemplate({
-        template,
-        context: {
-          arguments: {
-            id: '123',
-          },
-        },
-      }),
-    ).toEvaluateTo(expected);
-  });
-
-  it('should evaluate a template object', async () => {
-    // test that the template evaluates to the expected value as an object
+  it('should evaluate a template', async () => {
     await expect(
       appSyncMappingTemplate({
         template,
@@ -64,9 +31,7 @@ describe('Mapping Template', () => {
     });
   });
 
-  it('should evaluate a template snapshot as object', async () => {
-    // test that the template evaluates to the expected snapshot
-    // if the snapshot evaluates to an object, it is parsed before being saved
+  it('should evaluate a template snapshot', async () => {
     await expect(
       appSyncMappingTemplate({
         template,
@@ -79,9 +44,7 @@ describe('Mapping Template', () => {
     ).toEvaluateToSnapshot();
   });
 
-  it('should evaluate a template inline snapshot as object', async () => {
-    // test that the template evaluates to the expected inline snapshot
-    // if the snapshot evaluates to an object, it is parsed before being saved
+  it('should evaluate a template inline snapshot', async () => {
     await expect(
       appSyncMappingTemplate({
         template,
@@ -103,32 +66,83 @@ describe('Mapping Template', () => {
       }
     `);
   });
+});
 
-  it('should evaluate a template snapshot as string', async () => {
-    // test that the template evaluates to the expected snapshot
+describe('JS resolvers', () => {
+  const code = __dirname + '/assets/js-resolver.js';
+
+  it('should evaluate a js resolver', async () => {
     await expect(
-      appSyncMappingTemplate({
-        template: 'hello ${ctx.args.id}',
+      appSyncResolver({
+        code,
+        function: 'request',
         context: {
           arguments: {
-            id: '456',
+            id: '123',
+          },
+        },
+      }),
+    ).toEvaluateTo<DynamoDBGetItemRequest>({
+      operation: 'GetItem',
+      key: {
+        id: { S: '123' },
+      },
+    });
+
+    await expect(
+      appSyncResolver({
+        code,
+        function: 'response',
+        context: {
+          arguments: {
+            id: '123',
+          },
+          result: {
+            id: '123',
+            name: 'test',
+          },
+        },
+      }),
+    ).toEvaluateTo({
+      id: '123',
+      name: 'test',
+    });
+  });
+
+  it('should evaluate a js resolver with snapshot', async () => {
+    await expect(
+      appSyncResolver({
+        code,
+        function: 'request',
+        context: {
+          arguments: {
+            id: '123',
           },
         },
       }),
     ).toEvaluateToSnapshot();
   });
 
-  it('should evaluate a template inline snapshot', async () => {
-    // test that the template evaluates to the expected inline snapshot
+  it('should evaluate a js resolver inline snapshot', async () => {
     await expect(
-      appSyncMappingTemplate({
-        template: 'hello ${ctx.args.id}',
+      appSyncResolver({
+        code,
+        function: 'request',
         context: {
           arguments: {
             id: '789',
           },
         },
       }),
-    ).toEvaluateToInlineSnapshot(`"hello 789"`);
+    ).toEvaluateToInlineSnapshot(`
+      Object {
+        "key": Object {
+          "id": Object {
+            "S": "789",
+          },
+        },
+        "operation": "GetItem",
+      }
+    `);
   });
 });

examples/__tests__/assets/js-resolver.js

@@ -0,0 +1,13 @@
+import { get } from '@aws-appsync/utils/dynamodb';
+
+export const request = (ctx) => {
+  return get({
+    key: {
+      id: ctx.args.id,
+    },
+  });
+};
+
+export const response = (ctx) => {
+  return ctx.result;
+};

examples/__tests__/assets/mapping-template.vtl

@@ -0,0 +1,8 @@
+#set($id=$ctx.args.id)
+{
+  "version" : "2017-02-28",
+  "operation" : "GetItem",
+  "key" : {
+      "pk" : $util.dynamodb.toDynamoDBJson($id)
+  }
+}