Reorganized test_runner test apps.

tests/test_runner_apps/sample/doctests.py

@@ -0,0 +1,46 @@
+"""
+Doctest example from the official Python documentation.
+https://docs.python.org/3/library/doctest.html
+"""
+
+
+def factorial(n):
+    """Return the factorial of n, an exact integer >= 0.
+
+    >>> [factorial(n) for n in range(6)]
+    [1, 1, 2, 6, 24, 120]
+    >>> factorial(30)  # doctest: +ELLIPSIS
+    265252859812191058636308480000000...
+    >>> factorial(-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: n must be >= 0
+
+    Factorials of floats are OK, but the float must be an exact integer:
+    >>> factorial(30.1)
+    Traceback (most recent call last):
+        ...
+    ValueError: n must be exact integer
+    >>> factorial(30.0)  # doctest: +ELLIPSIS
+    265252859812191058636308480000000...
+
+    It must also not be ridiculously large:
+    >>> factorial(1e100)
+    Traceback (most recent call last):
+        ...
+    OverflowError: n too large
+    """
+
+    import math
+    if not n >= 0:
+        raise ValueError("n must be >= 0")
+    if math.floor(n) != n:
+        raise ValueError("n must be exact integer")
+    if n + 1 == n:  # catch a value like 1e300
+        raise OverflowError("n too large")
+    result = 1
+    factor = 2
+    while factor <= n:
+        result *= factor
+        factor += 1
+    return result