Unit testing docs (#3698)

* Updating library-tests and associated documentation to be more informative

* Fixing heading markup for updated unit testing docs

docs/testing.md

@@ -28,6 +28,29 @@ This dataset is a small extract and may not even contain all tags or edge cases.
 Furthermore this dataset is not in sync with what you see in up-to-date OSM maps or on the demo server.
 See the library tests for how to add new dataset dependent tests.
 
+To prepare the test data simply `cd test/data/` and then run `make`.
+
+### Running Tests
+
+To build the unit tests:
+
+```
+cd build
+cmake ..
+make tests
+```
+
+You should see the compiled binaries in `build/unit_tests`, you can then run each suite individually:
+
+```
+./engine-tests
+```
+
+For `library-tests` you will need to provide a path to the test data:
+
+```
+./library-tests ../../test/data/monaco.osrm
+```
 
 ## Cucumber
 

unit_tests/library/args.hpp

@@ -3,6 +3,7 @@
 
 #include <string>
 #include <vector>
+#include <iostream>
 
 inline std::vector<std::string> get_args()
 {
@@ -10,6 +11,11 @@ inline std::vector<std::string> get_args()
     const auto argc = boost::unit_test::framework::master_test_suite().argc - 1;
     const auto argv = boost::unit_test::framework::master_test_suite().argv + 1;
 
+    if (argc == 0)
+    {
+        std::cout << "You must provide a path to the test data, please see the unit testing docs" << std::endl;
+    }
+
     return {argv, argv + argc};
 }