add test for detecting loops in extended rulesets

tests/lib/config_tests.js

@@ -104,6 +104,20 @@ describe('lib', () => {
         expect(actual.rules['test-file-exists'].level).to.equals('off')
       })
 
+      it('should detect loops in extended rulesets', async () => {
+        const loopSelf = await Config.loadConfig(
+          path.join(__dirname, 'loop-self.yaml')
+        )
+        expect(loopSelf.rules).to.have.property('test-file-exists')
+        expect(loopSelf.rules['test-file-exists'].level).to.equals('error')
+
+        const loopB = await Config.loadConfig(
+          path.join(__dirname, 'loop-b.yaml')
+        )
+        expect(loopB.rules).to.have.property('test-file-exists')
+        expect(loopB.rules['test-file-exists'].level).to.equals('off')
+      })
+
       it('should throw error on non existant file', async () => {
         expect(Config.loadConfig('/does-not-exist')).to.eventually.throw(
           'ENOENT'

tests/lib/loop-a.yaml

@@ -0,0 +1,6 @@
+$schema: "../../rulesets/schema.json"
+extends: "./loop-b.yaml"
+version: 2
+rules:
+  test-file-exists:
+    level: error

tests/lib/loop-b.yaml

@@ -0,0 +1,6 @@
+$schema: "../../rulesets/schema.json"
+extends: "./loop-a.yaml"
+version: 2
+rules:
+  test-file-exists:
+    level: off

tests/lib/loop-self.yaml

@@ -0,0 +1,6 @@
+$schema: "../../rulesets/schema.json"
+extends: "./loop-self.yaml"
+version: 2
+rules:
+  test-file-exists:
+    level: error