After replacing Eclipse Luna with Eclipse Mars, the Run command (top bar button or CTRL+F11) does not execute a classes' main function or JUnit test anymore. Instead, the "Run configuration" menu is shown where it has to be configured manually. After a "restore defaults" in Window->Preferences->General->Keys, the last ran configuration is always executed, even if the active Tab contains a main class or a JUnit test case.
How can I restore the expected "Run" behaviour?
P.S.: Problem persists after upgrading from Eclipse 4.5.0 to 4.5.1.