feat(assertions): add function for verifying the number of matching resource properties

packages/@aws-cdk/assertions/README.md

@@ -76,6 +76,17 @@ in a template.
 template.resourceCountIs('Foo::Bar', 2);
 ```
 
+You can also count the number of resources of a specific type whose `Properties`
+section contains the specified properties:
+
+```ts
+template.resourcePropertiesCountIs('Foo::Bar', {
+  Foo: 'Bar',
+  Baz: 5,
+  Qux: [ 'Waldo', 'Fred' ],
+}, 1);
+```
+
 ## Resource Matching & Retrieval
 
 Beyond resource counting, the module also allows asserting that a resource with

packages/@aws-cdk/assertions/lib/private/resources.ts

@@ -32,11 +32,12 @@ export function hasResource(template: Template, type: string, props: any): strin
 }
 
 export function hasResourceProperties(template: Template, type: string, props: any): string | void {
-  // amended needs to be a deep copy to avoid modifying the template.
-  let amended = JSON.parse(JSON.stringify(template));
+  let amended = template;
 
   // special case to exclude AbsentMatch because adding an empty Properties object will affect its evaluation.
   if (!Matcher.isMatcher(props) || !(props instanceof AbsentMatch)) {
+    // amended needs to be a deep copy to avoid modifying the template.
+    amended = JSON.parse(JSON.stringify(template));
     amended = addEmptyProperties(amended);
   }
 
@@ -52,6 +53,27 @@ export function countResources(template: Template, type: string): number {
   return Object.entries(types).length;
 }
 
+export function countResourcesProperties(template: Template, type: string, props: any): number {
+  let amended = template;
+
+  // special case to exclude AbsentMatch because adding an empty Properties object will affect its evaluation.
+  if (!Matcher.isMatcher(props) || !(props instanceof AbsentMatch)) {
+    // amended needs to be a deep copy to avoid modifying the template.
+    amended = JSON.parse(JSON.stringify(template));
+    amended = addEmptyProperties(amended);
+  }
+
+  const section = amended.Resources ?? {};
+  const result = matchSection(filterType(section, type), Match.objectLike({
+    Properties: props,
+  }));
+
+  if (result.match) {
+    return Object.keys(result.matches).length;
+  }
+  return 0;
+}
+
 function addEmptyProperties(template: Template): Template {
   let section = template.Resources ?? {};
 

packages/@aws-cdk/assertions/lib/template.ts

@@ -8,7 +8,7 @@ import { checkTemplateForCyclicDependencies } from './private/cyclic';
 import { findMappings, hasMapping } from './private/mappings';
 import { findOutputs, hasOutput } from './private/outputs';
 import { findParameters, hasParameter } from './private/parameters';
-import { countResources, findResources, hasResource, hasResourceProperties } from './private/resources';
+import { countResources, countResourcesProperties, findResources, hasResource, hasResourceProperties } from './private/resources';
 import { Template as TemplateType } from './private/template';
 
 /**
@@ -71,6 +71,20 @@ export class Template {
     }
   }
 
+  /**
+   * Assert that the given number of resources of the given type and properties exists in the
+   * CloudFormation template.
+   * @param type the resource type; ex: `AWS::S3::Bucket`
+   * @param props the 'Properties' section of the resource as should be expected in the template.
+   * @param count number of expected instances
+   */
+  public resourcePropertiesCountIs(type: string, props: any, count: number): void {
+    const counted = countResourcesProperties(this.template, type, props);
+    if (counted !== count) {
+      throw new Error(`Expected ${count} resources of type ${type} but found ${counted}`);
+    }
+  }
+
   /**
    * Assert that a resource of the given type and properties exists in the
    * CloudFormation template.

packages/@aws-cdk/assertions/test/template.test.ts

@@ -124,6 +124,93 @@ describe('Template', () => {
     });
   });
 
+  describe('resourcePropertiesCountIs', () => {
+    test('resource exists', () => {
+      const stack = new Stack();
+      new CfnResource(stack, 'Resource', {
+        type: 'Foo::Bar',
+        properties: { baz: 'qux' },
+      });
+
+      const inspect = Template.fromStack(stack);
+      inspect.resourcePropertiesCountIs('Foo::Bar', { baz: 'qux' }, 1);
+
+      expect(() => {
+        inspect.resourcePropertiesCountIs('Foo::Bar', { baz: 'qux' }, 0);
+      }).toThrow('Expected 0 resources of type Foo::Bar but found 1');
+      expect(() => {
+        inspect.resourcePropertiesCountIs('Foo::Bar', { baz: 'qux' }, 2);
+      }).toThrow('Expected 2 resources of type Foo::Bar but found 1');
+      expect(() => {
+        inspect.resourcePropertiesCountIs('Foo::Bar', { baz: 'nope' }, 1);
+      }).toThrow('Expected 1 resources of type Foo::Bar but found 0');
+      expect(() => {
+        inspect.resourcePropertiesCountIs('Foo::Baz', { baz: 'qux' }, 1);
+      }).toThrow('Expected 1 resources of type Foo::Baz but found 0');
+    });
+    test('no resource', () => {
+      const stack = new Stack();
+
+      const inspect = Template.fromStack(stack);
+      inspect.resourcePropertiesCountIs('Foo::Bar', { baz: 'qux' }, 0);
+
+      expect(() => {
+        inspect.resourcePropertiesCountIs('Foo::Bar', { baz: 'qux' }, 1);
+      }).toThrow('Expected 1 resources of type Foo::Bar but found 0');
+    });
+    test('absent - with properties', () => {
+      const stack = new Stack();
+      new CfnResource(stack, 'Foo', {
+        type: 'Foo::Bar',
+        properties: { baz: 'qux' },
+      });
+
+      const inspect = Template.fromStack(stack);
+      inspect.resourcePropertiesCountIs('Foo::Bar', {
+        bar: Match.absent(),
+      }, 1);
+      inspect.resourcePropertiesCountIs('Foo::Bar', {
+        baz: Match.absent(),
+      }, 0);
+    });
+    test('absent - no properties', () => {
+      const stack = new Stack();
+      new CfnResource(stack, 'Foo', {
+        type: 'Foo::Bar',
+      });
+
+      const inspect = Template.fromStack(stack);
+      inspect.resourcePropertiesCountIs('Foo::Bar', {
+        bar: Match.absent(),
+        baz: 'qux',
+      }, 0);
+      inspect.resourcePropertiesCountIs('Foo::Bar', Match.absent(), 1);
+    });
+    test('not - with properties', () => {
+      const stack = new Stack();
+      new CfnResource(stack, 'Foo', {
+        type: 'Foo::Bar',
+        properties: { baz: 'qux' },
+      });
+
+      const inspect = Template.fromStack(stack);
+      inspect.resourcePropertiesCountIs('Foo::Bar', Match.not({
+        baz: 'boo',
+      }), 1);
+    });
+    test('not - no properties', () => {
+      const stack = new Stack();
+      new CfnResource(stack, 'Foo', {
+        type: 'Foo::Bar',
+      });
+
+      const inspect = Template.fromStack(stack);
+      inspect.resourcePropertiesCountIs('Foo::Bar', Match.not({
+        baz: 'qux',
+      }), 1);
+    });
+  });
+
   describe('templateMatches', () => {
     test('matches', () => {
       const app = new App();