Output individual and accumulated execution time of specs

[helpermethod]

Example:

up
  should change the current directory to the parent directory (0.001s)
  should change the current directory to the grandparent directory (0.001s)
  should fail if the current directory is the root directory (0.001s)
  should allow ~ as a valid basename (0.001s)

5 specs, 0 failed (0.053s)

See this SO question to get an idea on how to implement this.

[helpermethod]

Using date for measuring execution time has several flaws:

• The time measured is inaccurate
• The %s format specifier is not defined by POSIX
• The %N format specifier is not defined by POSIX and may not even be present on common platforms

Thus, some combination of the time builtin and the TIMEFORMAT environment variable is preferrable.

[helpermethod]

Measuring and accumulating now works but somehow a return code of 0 (i.e. success) is always returned (it seems that somehow the actual return code gets swallowed).

[helpermethod]

The return code of the command substitution got obscured by the local builtin (which has a return code by itself). Declaring the variable first (using the local keyword) and then assigning a value to it afterwards solved the problem.

[helpermethod]

As the time command was executed in a subshell the error_message global variable could not be set. Writing the output of time to a file and not executing it in a subshell may solve the problem.