diff --git a/lib/command/shell.js b/lib/command/shell.js
index 73a6927..bc71cd3 100644
--- a/lib/command/shell.js
+++ b/lib/command/shell.js
@@ -4,22 +4,22 @@ var ParentCommand = require('./spawn').Command,
 	inherits = require('util').inherits;
 
 function Command(params) {
+	params = params || {};
 	ParentCommand.call(this, params);
+	this.shell = params.shell || '/bin/sh';
 }
 
-exports.ShellCommand = Command;
+exports.Command = Command;
 
 inherits(Command, ParentCommand);
 
 
 /**
- * Executes `params.cmd` (e.g. 'echo 1 && echo 2') in `params.shell`
- * (e.g. '/bin/sh') with `params.options`
+ * Executes `params.cmd` (e.g. 'echo 1 && echo 2') in a `shell`
+ * (which was set at constructor) with `params.options`
  */
 Command.prototype.run = function(params, callback) {
-	if (!params.shell) return callback(new Error('`shell` is not set'));
-	if (!params.cmd) return callback(new Error('`cmd` is not set'));
-	ParentCommand.prototype.exec.call(this, {
-		cmd: params.shell, args: ['-c', params.cmd], options: params.options
+	ParentCommand.prototype.run.call(this, {
+		cmd: this.shell, args: ['-c', params.cmd], options: params.options
 	}, callback);
 };
diff --git a/lib/command/spawn.js b/lib/command/spawn.js
index 71bd9c8..d2e6710 100644
--- a/lib/command/spawn.js
+++ b/lib/command/spawn.js
@@ -27,6 +27,7 @@ Command.prototype.run = function(params, callback) {
 	var cmd = spawn(params.cmd, params.args, params.options);
 	cmd.stdout.on('data', function(data) {
 		if (self.isEmit) self.emit('stdout', data);
+		// TODO: join stdout only if flag is set
 		stdout += data;
 	});
 	cmd.stderr.on('data', function(data) {
@@ -34,11 +35,13 @@ Command.prototype.run = function(params, callback) {
 		cmd.kill();
 	});
 	cmd.on('exit', function(code) {
-		var err = null;
-		if (code !== 0) err = new Error(
-			'Scm command exits with non-zero code: ' + code
-		);
-		callback(err, stdout);
+		if (code !== 0) callback(new Error(
+			'Spawned command exits with non-zero code: ' + code
+		));
+	});
+	// TODO; callback should be called only once (port once from underscore)
+	cmd.on('close', function() {
+		callback(null, stdout);
 	});
 	return cmd;
 };
diff --git a/package.json b/package.json
index 6412bbe..0aca218 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,7 @@
     "nci": "bin/nci"
   },
   "scripts": {
-    "test": "mocha --bail --reporter=spec test"
+    "test": "mocha --bail --reporter=spec test/index"
   },
   "repository": {
     "type": "git",
diff --git a/test/commands/index.js b/test/commands/index.js
new file mode 100644
index 0000000..bd72714
--- /dev/null
+++ b/test/commands/index.js
@@ -0,0 +1,3 @@
+'use strict';
+
+require('./shell');
diff --git a/test/commands/shell.js b/test/commands/shell.js
new file mode 100644
index 0000000..e2691ce
--- /dev/null
+++ b/test/commands/shell.js
@@ -0,0 +1,31 @@
+'use strict';
+
+var expect = require('expect.js'),
+	ShellCommand = require('../../lib/command/shell').Command;
+
+describe('Shell command', function() {
+
+	var shellCommand;
+	it('Should be created without errors', function() {
+		shellCommand = new ShellCommand({
+			isEmit: true
+		});
+	});
+
+	it('Default shell should be sh', function() {
+		expect(shellCommand.shell).equal('/bin/sh');
+	});
+
+	it('echo "Hello world" should be done', function(done) {
+		var stdout = '';
+		shellCommand.on('stdout', function(data) {
+			stdout += data;
+		});
+		shellCommand.run({cmd: 'echo "Hello world"'}, function(err) {
+			expect(err).not.ok();
+			expect(stdout).equal('Hello world\n');
+			done();
+		});
+	});
+
+});
diff --git a/test/index.js b/test/index.js
new file mode 100644
index 0000000..b0a54db
--- /dev/null
+++ b/test/index.js
@@ -0,0 +1,4 @@
+'use strict';
+
+require('./commands');
+require('./scm')