Add example that demonstrates how to mock commands called by functions under test

doc/contributors.md

@@ -13,3 +13,4 @@ contributed in some way or another to shunit2.
 - Rocky Bernstein
 - [rugk](https://github.com/rugk)
 - wood4321 (of code.google.com)
+- [Rainer Poisel](https://github.com/rpoisel)

examples/lib.inc

@@ -0,0 +1,12 @@
+# available as examples/lib.inc
+
+myFunc() {
+	local msg="${1}"
+
+	local log
+	log="[$(date)] ${msg}"
+    echo "${log}"
+	if [ -n "${LOG_FILE_PATH}" ]; then
+        echo "${log}" 2>/dev/null >> "${LOG_FILE_PATH}"
+	fi
+}

examples/mock_cmd_complex_test.sh

@@ -0,0 +1,68 @@
+#!/bin/sh
+#
+# shUnit2 example for mocking commands.
+#
+# This example demonstrates a more flexible mechanism for mocking external
+# dependencies such as commands or functions.
+#
+# In this example, the behavior of the mocking function `date` can be changed
+# by defining the logic in a global variable `__ACTION`. Please note that this
+# approach would not work when executing tests in parallel due to race conditions
+# when reading/writing the global `__ACTION` variable.
+
+. ./lib.inc
+
+__ACTION="true"
+
+# dynamic mock (overrides original dependency)
+date() {
+	eval "${__ACTION}"
+}
+
+#dedicated function implementing the mock logic
+dying_date_func() {
+	exit 1
+}
+
+testMyFuncDateDies() {
+	__ACTION="dying_date_func"
+	LOG_FILE_PATH="/tmp/01.log"
+
+	local result rc exists contents
+	result=$(myFunc "some message")
+	rc=$?
+
+	assertEquals 0 "${rc}"
+	assertEquals "[] some message" "${result}"
+
+    exists=0
+    [ -e "/tmp/01.log" ] && exists=1
+    assertEquals 1 "${exists}"
+    contents=$(cat /tmp/01.log)
+    assertEquals "[] some message" "${contents}"
+}
+
+testMyFuncDoesSomethingMeaningful() {
+	__ACTION="echo \"now\""
+	LOG_FILE_PATH="/tmp/02.log"
+
+	local result rc exists contents
+	result=$(myFunc "some message")
+	rc=$?
+
+	assertEquals 0 "${rc}"
+	assertEquals "[now] some message" "${result}"
+
+    exists=0
+    [ -e "/tmp/02.log" ] && exists=1
+    assertEquals 1 "${exists}"
+    contents=$(cat /tmp/02.log)
+    assertEquals "[now] some message" "${contents}"
+}
+
+setUp() {
+	cp /dev/null /tmp/01.log
+	cp /dev/null /tmp/02.log
+}
+
+. ../shunit2

examples/mock_cmd_simple_test.sh

@@ -0,0 +1,50 @@
+#!/bin/sh
+#
+# shUnit2 example for mocking commands.
+#
+# This example demonstrates a simple mechanism for mocking external
+# dependencies such as commands or functions.
+#
+# In this example, the mocking function `date` behaves the same for
+# all tests.
+
+. ./lib.inc
+
+# static mock (overrides original dependency)
+date() {
+	echo "now"
+}
+
+testMyFuncMissingPath() {
+	unset LOG_FILE_PATH
+
+	local result rc
+	result=$(myFunc "some message")
+	rc=$?
+
+	assertEquals 0 "${rc}"
+	assertEquals "[now] some message" "${result}"
+}
+
+testMyFuncHappy() {
+	LOG_FILE_PATH="/tmp/01.log"
+
+	local result rc exists contents
+	result=$(myFunc "some message")
+	rc=$?
+
+	assertEquals 0 "${rc}"
+	assertEquals "[now] some message" "${result}"
+
+	exists=0
+	[ -e "/tmp/01.log" ] && exists=1
+	assertEquals 1 "${exists}"
+    contents=$(cat /tmp/01.log)
+	assertEquals "[now] some message" "${contents}"
+}
+
+setUp() {
+	cp /dev/null /tmp/01.log
+}
+
+. ../shunit2