Tests

Forge can run your tests with the forge test command. All tests are written in Solidity.

Forge will look for the tests anywhere in your source directory. Any contract with a function that starts with test is considered to be a test. Usually, tests will be placed in test/ by convention and end with .t.sol.

Here’s an example of running forge test in a freshly created project, that only has the default test:

$ forge test
No files changed, compilation skipped

Ran 2 tests for test/Counter.t.sol:CounterTest
[PASS] testFuzz_SetNumber(uint256) (runs: 256, μ: 30977, ~: 31288)
[PASS] test_Increment() (gas: 31303)
Suite result: ok. 2 passed; 0 failed; 0 skipped; finished in 8.33ms (8.03ms CPU time)

Ran 1 test suite in 9.39ms (8.33ms CPU time): 2 tests passed, 0 failed, 0 skipped (2 total tests)

You can also run specific tests by passing a filter:

$ forge test --match-contract ComplicatedContractTest --match-test test_Deposit
Compiling 24 files with Solc 0.8.10
Solc 0.8.10 finished in 1.06s
Compiler run successful!

Ran 2 tests for test/ComplicatedContract.t.sol:ComplicatedContractTest
[PASS] test_DepositERC20() (gas: 102193)
[PASS] test_DepositETH() (gas: 61414)
Suite result: ok. 2 passed; 0 failed; 0 skipped; finished in 1.28ms (1.51ms CPU time)

Ran 1 test suite in 5.59ms (1.28ms CPU time): 2 tests passed, 0 failed, 0 skipped (2 total tests)

This will run the tests in the ComplicatedContractTest test contract with testDeposit in the name. Inverse versions of these flags also exist (--no-match-contract and --no-match-test).

You can run tests in filenames that match a glob pattern with --match-path.

$ forge test --match-path test/ContractB.t.sol
Compiling 1 files with Solc 0.8.10
Solc 0.8.10 finished in 1.02s
Compiler run successful!

Ran 1 test for test/ContractB.t.sol:ContractBTest
[PASS] testExample() (gas: 257)
Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 341.18µs (47.73µs CPU time)

Ran 1 test suite in 5.51ms (341.18µs CPU time): 1 tests passed, 0 failed, 0 skipped (1 total tests)

The inverse of the --match-path flag is --no-match-path.

Logs and traces

The default behavior for forge test is to only display a summary of passing and failing tests. You can control this behavior by increasing the verbosity (using the -v flag). Each level of verbosity adds more information:

  • Level 2 (-vv): Logs emitted during tests are also displayed. That includes assertion errors from tests, showing information such as expected vs actual.
  • Level 3 (-vvv): Stack traces for failing tests are also displayed.
  • Level 4 (-vvvv): Stack traces for all tests are displayed, and setup traces for failing tests are displayed.
  • Level 5 (-vvvvv): Stack traces and setup traces are always displayed.

Watch mode

Forge can re-run your tests when you make changes to your files using forge test --watch.

By default, only changed test files are re-run. If you want to re-run all tests on a change, you can use forge test --watch --run-all.