Add tests for count & groupBy, and fix groupBy

knex.js

@@ -679,7 +679,7 @@
 
     // Adds a `group by` clause to the query.
     groupBy: function() {
-      this.groups = this.groups.concat(_.toArray(arguments));
+      this.groups = (this.groups||[]).concat(_.toArray(arguments));
       return this;
     },
 

test/lib/aggregate.js

@@ -9,4 +9,12 @@ module.exports = function(Knex, dbName, resolver) {
 
   });
 
-};
+  it('has a count', function(ok) {
+      Knex('accounts').count('id').then(resolver(ok), ok);
+  });
+
+  it("support the groupBy function", function(ok) {
+      Knex('accounts').count('id').groupBy('logins').then(resolver(ok), ok);
+  });
+
+};

test/shared/output.js

@@ -504,6 +504,34 @@ module.exports = {
         bindings: []
       }
     },
+    'aggregate.2': {
+      mysql: {
+        sql: ['select count(`id`) as aggregate from `accounts`'],
+        bindings: []
+      },
+      postgres: {
+        sql: ['select count("id") as aggregate from "accounts"'],
+        bindings: []
+      },
+      sqlite3: {
+        sql: ['select count("id") as aggregate from "accounts"'],
+        bindings: []
+      }
+    },
+    'aggregate.3': {
+      mysql: {
+        sql: ['select count(`id`) as aggregate from `accounts` group by `logins`'],
+        bindings: []
+      },
+      postgres: {
+        sql: ['select count("id") as aggregate from "accounts" group by "logins"'],
+        bindings: []
+      },
+      sqlite3: {
+        sql: ['select count("id") as aggregate from "accounts" group by "logins"'],
+        bindings: []
+      }
+    },
     'joins.1': {
       mysql: {
         sql: ['select `accounts`.*, `test_table_two`.`details` from `accounts` inner join `test_table_two` on `accounts`.`id` = `test_table_two`.`account_id`'],
@@ -1961,6 +1989,34 @@ module.exports = {
         aggregate: 10
       }]
     },
+    'aggregate.2': {
+      mysql: [{
+        aggregate: 6
+      }],
+      postgres: [{
+        aggregate: 6
+      }],
+      sqlite3: [{
+        aggregate: 6
+      }]
+    },
+    'aggregate.3': {
+      mysql: [{
+        aggregate: 2
+      }, {
+        aggregate: 4
+      }],
+      postgres: [{
+        aggregate: 2
+      }, {
+        aggregate: 4
+      }],
+      sqlite3: [{
+        aggregate: 2
+      }, {
+        aggregate: 4
+      }]
+    },
     'joins.1': {
       mysql: [{
         id: 1,