This file is really nothing more than all the tests coalesced into a single HTML file. To run a test, open a Javascript console and execute, for instance,

tc = new SimpleDrawingTestCase() ;

    tc.runTest("testDrawSimpleRangePlusOne")

(execution method #1, by string)
tc.runTest(tc.testDrawSimpleRangePlusOne) (execution method #2, by function reference)

Alternatively you can use query args:

testCase - for the name of the test case
test - for the name of the test (use command=runTest)
command - either runTest or runAllTests.

Example: local.html?testCase=ScrollingDivTestCase&test=testNestedDiv_Scrolled&command=runTest