Add support for keys command (#92)

@pivotal-csaa thanks! 👍

package.json

@@ -54,6 +54,7 @@
   "dependencies": {
     "bluebird": "3.4.1",
     "lodash": "4.14.1",
+    "minimatch": "^3.0.2",
     "redis-commands": "1.2.0"
   }
 }

src/commands/index.js

@@ -18,6 +18,7 @@ export * from './hstrlen';
 export * from './hvals';
 export * from './incr';
 export * from './incrby';
+export * from './keys';
 export * from './rename';
 export * from './sadd';
 export * from './set';

src/commands/keys.js

@@ -0,0 +1,5 @@
+import minimatch from 'minimatch';
+
+export function keys(globString) {
+  return Object.keys(this.data).filter((key) => minimatch(key, globString));
+}

test/commands/keys.js

@@ -0,0 +1,34 @@
+import expect from 'expect';
+
+import MockRedis from '../../src';
+
+describe('keys', () => {
+  it('should return an empty array if there are no keys', () => {
+    const redis = new MockRedis();
+
+    return redis.keys('*').then(result => expect(result).toEqual([]));
+  });
+
+  it('should return all data keys', () => {
+    const redis = new MockRedis({
+      data: {
+        foo: 'bar',
+        baz: 'quux',
+      },
+    });
+
+    return redis.keys('*').then(result => expect(result).toEqual(['foo', 'baz']));
+  });
+
+  it('should only return keys matching the given pattern', () => {
+    const redis = new MockRedis({
+      data: {
+        foo: 'bar',
+        baz: 'quux',
+        flambé: 'baked alaska',
+      },
+    });
+
+    return redis.keys('f*').then(result => expect(result).toEqual(['foo', 'flambé']));
+  });
+});