Add tests and tweak apply

.gitignore

@@ -1,3 +1,4 @@
 node_modules/
 coverage/
 npm-*.log
+debug.log

index.js

@@ -80,18 +80,22 @@ class RefreshingConfig extends EventEmitter {
   }
 
   apply(patches) {
-    // Snapshot the properties/name and apply the patches. If a changed property is still present,
+    // Snapshot the property names and apply the patches. If a changed property is still present,
     // it was changed so set. If it is now missing, delete it.
-    const newValues = Object.assign({}, this.values);
-    patch.apply(newValues, patches);
+    return this.refreshIfNeeded().then(() => {
+      const oldKeys = Object.getOwnPropertyNames(this.values);
+      patch.apply(this.values, patches);
       const affected = this._getAffectedProperties(patches);
       return Q.all(affected.map(key => {
-      if (newValues[key] === undefined) {
-        return this.delete(key);
-      } else {
-        return this.set(key, newValues[key]);
+        if (this.values[key] !== undefined) {
+          return this.set(key, this.values[key]);
         }
+        if (oldKeys.includes(key)) {
+          return this.delete(key);
+        }
+        return Q();
       }));
+    });
   }
 
   _getAffectedProperties(patches) {

test/index-test.js

@@ -1,7 +1,7 @@
+const chai = require('chai');
 const clone = require('clone');
 const events = require('events');
 const Q = require('q');
-const chai = require('chai');
 const sinon = require('sinon');
 chai.should();
 
@@ -204,6 +204,27 @@ describe('RefreshingConfig', () => {
     target.withExtension(null).should.equal(target);
     target.withExtension({}).should.equal(target);
   });
+  it('applies patches correctly', () => {
+    const store = {
+      getAll: sinon.stub().returns(Q({ foo: 'bar', test: 42 })),
+      set: sinon.stub().returns(Q()),
+      delete: sinon.stub().returns(Q())
+    };
+    const target = new config.RefreshingConfig(store);
+    const patches = [
+      { op: 'add', path: '/first', value: 'value' },
+      { op: 'replace', path: '/foo', value: 'fred' },
+      { op: 'remove', path: '/test' },
+      { op: 'remove', path: '/test2' }
+    ];
+    return target.apply(patches).then(() => {
+      store.set.calledTwice.should.be.true;
+      store.set.firstCall.calledWith('first', 'value').should.be.true;
+      store.set.secondCall.calledWith('foo', 'fred').should.be.true;
+      store.delete.calledOnce.should.be.true;
+      store.delete.firstCall.calledWith('test').should.be.true;
+    });
+  });
 });
 
 describe('AlwaysRefreshPolicy', () => {