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wiki/GoogleTestAdvancedGuide.wiki

@@ -810,10 +810,36 @@ _Availability:_ Linux, Windows, Mac.
 = Value Parameterized Tests =
 
 _Value-parameterized tests_ allow you to test your code with different
-parameters without writing multiple copies of the same test.  This is
-useful in a number of situations, for example:
+parameters without writing multiple copies of the same test. 
+
+Suppose you write a test for your code and then realize that your code is affected by a presence of a Boolean command line flag.
+
+{{{
+TEST(MyCodeTest, TestFoo) {
+  // A code to test foo().
+}
+}}}
+
+Usually people factor their test code into a function with a Boolean parameter in such situations. The function sets the flag, then executes the testing code.
+
+{{{
+void TestFooHelper(bool flag_value) {
+  flag = flag_value;
+  // A code to test foo().
+}
+
+TEST(MyCodeTest, TestFooo) {
+  TestFooHelper(false);
+  TestFooHelper(true);
+}
+}}}
+
+But this setup has serious drawbacks. First, when a test assertion fails in your tests, it becomes unclear what value of the parameter caused it to fail. You can stream a clarifying message into your `EXPECT`/`ASSERT` statements, but it you'll have to do it with all of them. Second, you have to add one such helper function per test. What if you have ten tests? Twenty? A hundred?
+
+Value-parameterized tests will let you write your test only once and then easily instantiate and run it with an arbitrary number of parameter values.
+
+Here are some other situations when value-parameterized tests come handy:
 
-   * You have a piece of code whose behavior is affected by one or more command-line flags. You want to make sure your code performs correctly for various values of those flags.
    * You wan to test different implementations of an OO interface.
    * You want to test your code over various inputs (a.k.a. data-driven testing). This feature is easy to abuse, so please exercise your good sense when doing it!