Created Test fixtures (markdown)

Test-fixtures.md

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+Sometimes you'll have the need to group a number of tests together and provide some context to that group of tests, for example an initial state or some shared variable. This is done by using a test fixture. In Catch, you define the test fixture as a simple structure:
+
+```c++
+class UniqueTestsFixture {
+  private:
+   static int uniqueID;
+  protected:
+   DBConnection conn;
+  public:
+   UniqueTestsFixture() : conn(DBConnection::createConnection("myDB")) {
+   }
+  protected:
+   int getID() {
+     return ++uniqueID;
+   }
+ };
+
+ int UniqueTestsFixture::uniqueID = 0;
+
+ TEST_CASE_METHOD(UniqueTestsFixture, "Create Employee/No Name", "[create]") {
+   REQUIRE_THROWS(conn.executeSQL("INSERT INTO employee (id, name) VALUES (?, ?)", getID(), ""));
+ }
+ TEST_CASE_METHOD(UniqueTestsFixture, "Create Employee/Normal", "[create]") {
+   REQUIRE(conn.executeSQL("INSERT INTO employee (id, name) VALUES (?, ?)", getID(), "Joe Bloggs"));
+ }
+```
+
+The two test cases here will create uniquely-named derived classes of UniqueTestsFixture and thus can access the `getID()` protected method and `conn` member variables. This ensures that both the test cases are able to create a DBConnection using the same method (DRY principle) and that any ID's created are unique such that the order that tests are executed does not matter.