environment

(i)

Java - Netbeans, Eclipse, IntellijIDEA

C# - VisualStudio, MonoDevelop, SharpDevelop

JavaScript - Eclipse, WebStorm, Aptana

Swift - Xcode, Scade, AppCode

(ii)

Repl.it, JsFiddle, Ideone

(iii)

Java - JUnit

C# - Microsoft Unit Testing Framework for Managed Code

JavaScript - JUnit

Swift - XCtest

(iv)

Java - Java Package Manager

C# - NuGet

JavaScript - Bower

Swift - Package Manager