updating the test filename to match the command

test/commands/exists.spec.js

@@ -0,0 +1,40 @@
+'use strict';
+
+var config = require("../lib/config");
+var helper = require("../helper");
+var redis = config.redis;
+
+describe("The 'exists' method", function () {
+
+    helper.allTests(function(parser, ip, args) {
+
+        describe("using " + parser + " and " + ip, function () {
+            var client;
+
+            beforeEach(function (done) {
+                client = redis.createClient.apply(redis.createClient, args);
+                client.once("ready", function () {
+                    client.flushdb(done);
+                });
+            });
+
+            it('returns 1 if the key exists', function (done) {
+                client.set('foo', 'bar');
+                client.EXISTS('foo', helper.isNumber(1, done));
+            });
+
+            it('returns 1 if the key exists with array syntax', function (done) {
+                client.set('foo', 'bar');
+                client.EXISTS(['foo'], helper.isNumber(1, done));
+            });
+
+            it('returns 0 if the key does not exist', function (done) {
+                client.exists('bar', helper.isNumber(0, done));
+            });
+
+            afterEach(function () {
+                client.end(true);
+            });
+        });
+    });
+});