To debug one failing Go test with Atlas, you shrink the problem before you reason about it. Atlas runs just that test through the bash tool using the framework's filter flag, so go test -run TestCreateOrder ./internal/store produces output small enough to hold in your head instead of a full module's worth of FAIL blocks. Atlas then reads the test and the code it exercises, and walks the call path with the lsp tool's goToDefinition and findReferences operations to see what the assertion actually depends on. Because Atlas's bash is a real shell, every debugging lever you would reach for by hand is available: add temporary t.Logf output with edit, re-run with go test -v, narrow the filter further. The fix lands in the production code with edit, or with apply_patch when it spans several hunks, and the assertion stays honest.
How do you isolate a single failing Go test so the output is readable?
Atlas runs just the failing test with the bash tool, using the framework's filter flag, which is step 1 of the documented workflow. In Go that is go test -run TestCreateOrder ./internal/store, which drops a whole module's FAIL blocks down to a single assertion diff you can reason about in one pass.
Isolation is the first move because signal-to-noise decides everything downstream. A full go test ./... run in a Go module with 40 packages buries the one failure you care about under passing package lines and unrelated skips. The -run filter cuts to exactly one test, and Atlas's bash tool is a real shell, so the filter flag, the package path, and any build tags you need all work exactly as they do in your own terminal. Every bash call is permission-gated against allow, ask, and deny rules before it runs, so the go test command that executes is the one you approved.
How does Atlas walk the Go call path from a failing assertion to the real cause?
Atlas reads the failing Go test and the module it exercises, then uses 2 lsp operations, goToDefinition and findReferences, to walk the call path. goToDefinition follows the interface method in internal/store to its concrete implementation, which is where Go bugs usually live and where the test never looks.
Go's interfaces make the call path non-obvious from the test alone. A test that exercises a Store interface tells you nothing about which struct actually satisfies it at runtime, and reading the test file will never reveal that. The lsp tool's goToDefinition operation jumps from the interface method to the implementation, and findReferences shows every other caller that reaches the same code, which often explains why the behavior is what it is. Atlas indexes code by AST declarations using tree-sitter, not blind line windows, so each hop returns a whole Go function rather than a window that clips the error branch you needed to see.
How do you test a hypothesis about a failing Go test without a debugger?
Atlas forms a hypothesis and checks it, step 3 of the documented workflow, using the same levers a Go developer uses by hand: add a temporary t.Logf with the edit tool, then re-run go test -v -run TestCreateOrder through bash so the verbose output prints. Atlas's bash is a real shell, so nothing is simulated.
Debugging a Go test is mostly a loop of guess, instrument, observe. Atlas does exactly that: edit adds temporary logging at the suspect line, bash re-runs the single test with a verbose flag so Go actually emits the log lines, and the output either confirms the hypothesis or kills it. The advantage over a manual loop is bookkeeping, not magic: Atlas remembers which temporary logging it added and removes it at the end. Atlas computes a unified diff for every file edit and surfaces it for approval before writing, so even a throwaway t.Logf is a change you saw.
When should Atlas use apply_patch instead of edit for a Go fix?
Atlas fixes Go production code with the edit tool for a single-site change and switches to apply_patch when the fix spans several hunks. Chaining brittle edits across 3 functions in internal/store/orders.go is how a partial fix lands, while apply_patch expresses the whole change as 1 anchored patch instead.
A Go bug that turns out to be a missing error check often is not one line. The fix touches the function that swallowed the error, the caller that assumed success, and the interface signature in between. edit is right for one site. apply_patch is right for the multi-hunk case, because it applies the change as a unit with anchored context rather than as a sequence of independent replacements that could half-succeed. Atlas snapshots file changes as git patches, so a fix that made the Go module worse can be diffed and rolled back rather than reverted by hand.
How do you confirm a Go fix without breaking the rest of the module?
Atlas re-runs the single test with go test -run first, then the full go test ./... suite, and removes any temporary logging it added. Fixing 1 Go test while breaking 2 others is a net loss, and the full suite is the only thing that catches it before the commit.
The closing sequence is deliberate. The isolated go test -run confirms the specific fix worked. The full go test ./... run confirms the fix did not regress another package in the module, which is a real risk when the change touched a shared interface or a package-level variable. Removing the temporary t.Logf lines keeps the diff honest, gofmt keeps the changed files formatted, and go mod stays untouched unless the fix genuinely required a dependency change. Atlas reads git branches, status, and diffs, and can stage and create commits on your behalf once ./... is green.
Step by step
- 01Run atlas in a Go module that has a go.mod, so Atlas can read your packages, interfaces, and go.sum dependencies.
- 02Run just the failing test with the bash tool using the framework's filter flag, for example go test -run TestCreateOrder ./internal/store, so the output is small enough to reason about.
- 03Read the failing Go test and the module it exercises, then use the lsp tool's goToDefinition operation to jump from the interface method to the concrete implementation.
- 04Run the lsp tool's findReferences operation on the suspect function to see every other caller that reaches the same code path.
- 05Form a hypothesis and check it: add temporary t.Logf output with the edit tool, or re-run through bash with go test -v so the verbose output actually prints.
- 06Fix the Go production code with the edit tool, not the assertion; if the change spans several hunks across internal/, use apply_patch instead of chaining brittle edits.
- 07Re-run the single test with go test -run to confirm the fix, then run the full go test ./... suite to check the rest of the module.
- 08Remove every temporary logging line you added, run gofmt over the changed files, and review the unified diff Atlas surfaces before committing.
Frequently asked questions
- how to debug a single failing go test with an AI coding agent
- Isolate it first. Atlas runs go test -run TestName ./package through its bash tool so the output is small, reads the test and the code it exercises, walks the call path with the lsp tool's goToDefinition and findReferences operations, then fixes the production code with edit.
- can atlas run go test with a verbose flag
- Yes. Atlas's bash tool is a real shell, so go test -v, the -run filter, build tags, and environment variables all work exactly as they do in your own terminal. Every bash call is permission-gated against allow, ask, and deny rules before it runs.
- how do i find the concrete implementation behind a go interface in a failing test
- Use the lsp tool's goToDefinition operation. A Go test that exercises an interface tells you nothing about which struct satisfies it at runtime, and goToDefinition jumps to the implementation. findReferences then shows every other caller reaching that code.
- will atlas change my test assertion to make a go test pass
- The documented workflow is to find why the test fails and fix the code, not the assertion. Atlas edits the Go production code, and every edit is surfaced as a unified diff for approval before it is written, so an assertion change would be visible in review.
- atlas edit vs apply_patch for a go bug fix
- Use edit for a single-site change. Use apply_patch when the fix spans several hunks, for example when a missing error check forces changes to the function, its caller, and the interface signature between them. apply_patch applies the change as one anchored unit.
- does atlas remove the debug logging it adds to go code
- Yes. The documented final step is to re-run the single test, then the full suite, and remove any temporary logging you added. Atlas computes a unified diff for every file edit, so any leftover t.Logf would be visible in the diff you approve.
- should i run the full go test suite after fixing one test
- Yes. Fixing one Go test while breaking two others is a net loss, and a change to a shared interface or package-level variable is exactly the kind of fix that regresses another package. Run go test ./... after the isolated test goes green.
- does atlas work with go modules and gofmt
- Atlas is documented for use with Go modules, interfaces, and the go test toolchain. Run atlas in a module with a go.mod, and it reads your packages, interfaces, and go.sum dependencies. gofmt is the formatter and go mod is the package manager in that toolchain.
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Install AtlasRelated guides
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