SpectNet IDE

Visual Studio 2017/2019 integrated ZX Spectrum IDE for the Community

Unit Testing » The Testing Process

The Testing Process

You already learned that tests are organized into a hierarchy of test files, test sets, tests, and parameterized test cases. In this section you will learn how the test engine manages these tests.

The testing process start with the compilation of tests. During this step, all tests are turned into execution plans. If there is any compilation error, the engine won’t start running the tests.

The unit of execution is the test set. Test sets are entirelly independent of each other. You can run them in any sequence; the order won’t change whether they fail or succeed. SpectNetIde loops through all test files declared in the project (you cannot assume deterministic order), and runs all test sets in their declaration order within a file.

Each test sets creates and starts a Spectrum virtual machine, and pauses it when the machine reaches its main execution cycle. The point a machine is paused depends on its type (different for Spectrum 48K, 128K, +3E), and also the mode the machine runs. For example, in a Spectrum 128K machine you can run tests in BASIC 128 mode or in Spectrum 48K mode.

Right now, the unit test engine supports only Spectrum 48K mode, but soon you will be able to use the other modes, too.

Running a Test Set

Every test within a test set uses this virtual machine. This machine is paused every time a test completes (either successfully, with a failure, or in aborted state). If a test disrupts the machine’s memory (for example, it changes the code being tested), the behavior of a particular test may prevent the subsequent test from running properly. This demeanor of test sets is intentional.

The engine uses these steps to run the tests defined within a tes set:

  1. After the Spectrum machine reaches its startup state and pauses, the engine copies the compiled source code into the memory.
  2. If the test set declares an init section, the engine sets up the registers and flags accordingly, copies byte array values into the memory. While initializing, it follows the order of init assignments.
  3. The engine loops through the nested test blocks in their declaration order, and executes them.
  4. When all tests are completed, the engine stops the virtual machine and disposes its state.

Running a Test and Parameterized Cases

To run a single test, the engine follows these steps:

  1. If the test has a setup declaration, the engine invokes the Setup code. If that code fails — it exceeds the timeout — the engine aborts the test.
  2. If the test has a single default case, the engine runs that case. If the test has multiple cases, the engine iterates through all cases in their declaration order.
  3. Provided the test has a cleanup section, the engine invokes the Cleanup code. If this code exceeds the timeout, the Cleanup code aborts the test.

According to this method, it might happen that all tests run successfully and still the test is aborted, because its Cleanup code fails. This behavior is intentional: a faulty cleanup code may influence the subsequent tests.

The engine carries out the same steps for a default test case and parameterized test cases. If there are more cases, these steps are executed in a loop:

  1. Provided there are arrange declarations, the engine sets up the registers and flags accordingly, copies byte array values into the memory — in the order of their declaration. If any arrange assignment fails, the test is aborted.
  2. The engine invokes the act code. If it completes within the timeout, the testing process goes on; otherwise, the test is aborted.
  3. If there is no assert section, the test is successful.
  4. If there’s an assert section, the engine evaluates all expresssions within until it iterates through all or one of the expression evaluates to false.
  5. A false assertion value completes the test as failed. If all assertions are true, the test is successful.

Side effects

A test can have test options (such as timeout, di, or ei). The engine uses these values whenever it invokes Z80 code, independently whether that is setup, act, or cleanup. Between these code invocations, the engine simply pauses the Spectrum virtual machine and starts it again. There is one special action the test engine takes: if a code is invoked with halt, the test removes the CPU from its halted state before the next test.

Again, the code is injected into the virtual machine only once, at the start of a test set. If any code changes the memory, it may disrupt the test code, and thus remaining test cases in the test set may fail of even may be aborted. Nonetheless, these tests won’t cause any harm in your project, they just cause tests fail.

For example, the following code disrupts the Spectrum virtual machine, because it restarts it, and so it causes the clearing the RAM:

testset Crashing
    source "../Z80CodeFiles/CodeSamples.z80asm";

    test CrashingCode
        with timeout 1000;
        act call #0000;

Running it will abort the test after a second.

Using Callstub

When you invoke the code with the call instruction, the test engine generates a stub that call your subroutine. By default, the engine places three bytes with a Z80 CALL instruction to the #5BA0 address, that is an empty area within the ZX Spectrum system variables (printer buffer in ZX Spectrum 48K). If you do not want to use this address for a stub, you can change it with the callstub attribute of a test set:

testset Introduction
    source "../Z80CodeFiles/CodeSamples.z80asm";
    callstub #8000;

    // --- Other test code omitted

This sample code instructs the engine to use the #8000 address to generate the stub. Be careful with using your custom stub!

  • First, do not forget to provide 3 bytes that the test engine can override.
  • Second, take care that you do not declare a call code invocation that addresses a routine starting at the callstub + 3 address. The test engine checks if your call is completed so that it compares PC with callstub + 3.

This is a pattern you can use with your own custom callstub:

.org #8000

; --- Here is some code

; --- We reserve 4 bytes
    .defs 4;
; --- SomeRoutine starts at CallstubAddress + 4
; --- Add routine code here

Now, you can define a test line this:

testset Introduction
    source "../Z80CodeFiles/CodeSamples.z80asm";
    callstub CallstubAddress;

        // ...
        act call SomeRoutine;