With solana-program-test crate, what accounts/programs will be included in the environment by default when starting test?

Question

I want to use solana-program-test crate to do some integrated tests.

I've read the code of some sample Solana programs in the official solana-program-library repo on GitHub. Inside, there's an example program called transfer-tokens, that demonstrates how to perform a CPI to Token Program to transfer SPL tokens.

The Rust test file is here. I'm wondering why the Token Program isn't added to the test environment by calling program_test.add_program(). In my opinion, the Token Program has no difference with the custom sample program, in that both 2 programs are not native programs like System Program. The Token Program is but a normal program that is implemented by Solana Dev Team. Why is the custom program necessary to be added (here it's added in ProgramTest::new() that calls add_program() inside), while the Token Program is not explicitly added?

Also, from the solana-program-test crate's doc, I learn that I can specify the fixtures of the test environment. I'm wondering if there's a more detailed and official doc that describes how fixtures work in solana-program-test crate? The Rust doc only introduces the fixtures with no more than 100 words.

Answer 1

solana-program-test adds a few programs by default to help with local development and so that devs don't need as many fixtures.

You can find those programs at https://github.com/anza-xyz/agave/blob/master/program-test/src/programs.rs, and they include:

• spl-token
• spl-token-2022
• spl-memo-1.0
• spl-memo-3.0
• spl-associated-token-account