how to triage a wall of failing ScalaTest specs

Run ScalaTest via sbt test through Atlas's bash tool, then grep the saved log to group failures by root cause rather than by spec name. Atlas records one todowrite entry per distinct cause with status pending, and fixes them one at a time with edit, re-running only the affected specs.

why is my sbt test output truncated in Atlas

The Atlas bash tool truncates displayed output at 2000 lines or 50 KB so a full sbt test run does not flood the model's context. The complete log is written to a retained file and the path is reported in the ...output truncated... header, so read it to see everything.

how do I stop Atlas from killing a slow sbt test run

Pass a generous timeout in milliseconds to the bash tool. A first sbt test often spends minutes in incremental compilation, macro expansion, and implicit resolution before ScalaTest prints anything, and a run killed at that point looks like a failure when it was only slow.

should I group Scala test failures by test name or by cause

By cause. In Scala a single changed implicit in a package object or a modified case class field can redden a dozen specs at once. Atlas greps the saved sbt test log for shared exception types and compiler errors, then records one todowrite entry per distinct root cause.

does Atlas re-run the whole Scala suite after every fix

No. Atlas fixes the causes one at a time with edit and re-runs only the affected ScalaTest specs via sbt test between changes, which keeps the loop fast on a large multi-module build. The full sbt test runs once at the end to confirm nothing regressed.

how do I know an Atlas test fix is real and not just a weakened assertion

Atlas computes a unified diff for every file edit and surfaces it for approval before writing, so every change to a .scala file under src/test/scala is reviewed before it lands. Atlas also snapshots file changes as git patches, so a bad fix can be diffed and rolled back.

atlas Scala sbt setup

Run atlas in a project with a build.sbt. Atlas reads your traits, implicits, and sbt modules, and can refactor to typeclasses or add ScalaTest cases, with the diff reviewed first. Tests run as ScalaTest via sbt test and formatting through scalafmt.

where does Atlas save the full sbt test log

The Atlas bash tool writes the complete log to a retained file and names the path in the truncation header of its output. Read that file to see every ScalaTest failure, including the ones cut off by the 2000 line or 50 KB display limit.

Run the Test Suite and Triage the Failures in Scala with Atlas (2026)

Atlas turns a wall of red ScalaTest output into a prioritized list of distinct root causes. The Atlas bash tool runs ScalaTest via sbt test with a generous timeout in milliseconds so a slow sbt run is not killed mid-compile, truncates its displayed output at 2000 lines or 50 KB, writes the complete log to a retained file, and tells you the path. Triage then happens with grep over the whole saved log, and each distinct cause becomes one todowrite entry with status pending rather than a failure nobody remembers.

How does Atlas run a Scala test suite without flooding the model's context?

Atlas runs ScalaTest via sbt test through the bash tool, which truncates displayed output at 2000 lines or 50 KB, writes the complete log to a retained file, and tells you the path. A full sbt test run on a multi-module Scala build produces far more output than any model should read.

Scala test output is uniquely verbose. sbt prints compilation progress for every module in build.sbt, ScalaTest prints a line per test, and a single failing assertion can produce a 200 line diff of a case class. Feeding all of that into a model is both expensive and counterproductive. The Atlas bash tool caps what enters context at 2000 lines or 50 KB while retaining the entire log on disk. The truncation header names the file. That design is what makes triage lossless: the model works from a summary, then greps the complete log for the parts that matter, rather than reasoning over a tail that cut off the first three failures.

Why does Atlas pass a generous timeout to sbt test?

Atlas passes a generous timeout in milliseconds to the bash tool when running ScalaTest via sbt test, because sbt must often compile the whole project before the 1st test even runs. A Scala suite killed at the default timeout looks like a failure when it was only slow.

The first sbt test in a session is rarely fast. Incremental compilation has to warm up, macros expand, implicit resolution runs, and a large Scala module can spend minutes in the compiler before ScalaTest prints its first green dot. An agent that kills that run and reports a failure has produced a false negative, and false negatives during triage are worse than useless. The Atlas bash tool takes an explicit timeout in milliseconds, so the sbt run gets the time it actually needs. The retained-log behavior applies regardless: even a long run that eventually fails leaves a complete log on disk for grep.

How do I group Scala test failures by root cause instead of by test name?

Atlas groups ScalaTest failures by root cause with grep over the saved log, not by test name. Twelve red ScalaTest specs frequently come from 2 causes: one implicit that no longer resolves, and one shared fixture that changed. Grouping by test name would produce 12 tasks instead of 2.

Root-cause grouping is the substance of triage. In Scala the same underlying break tends to fan out widely: a changed implicit in a package object turns every spec that summons it red, a modified case class field breaks every ScalaTest matcher comparing it, and a failed compile in one sbt module fails every downstream module's tests at once. Atlas greps the saved log for the exception types, the shared message strings, and the compiler errors, and clusters the failures accordingly. Atlas also searches code with hybrid semantic and keyword retrieval fused by reciprocal rank fusion and indexes code by AST declarations using tree-sitter, not blind line windows, so tracing a cause from the log back to the trait or implicit that owns it is a single query.

How does Atlas track and fix the distinct Scala failures it found?

Atlas records 1 todowrite entry per distinct root cause, with status pending, so the fixes are tracked instead of forgotten. Each cause is then fixed with the edit tool, re-running only the affected ScalaTest specs via sbt test between changes rather than the whole Scala suite every time.

The todowrite list is the memory of the triage. Each entry names a root cause, not a test name, so closing it means the class of failure is gone rather than one red spec turned green. Atlas fixes them one at a time with the edit tool, whose replacer cascade refuses ambiguous multi-match replacements, and re-runs the narrow ScalaTest selection through the bash tool between changes. Running a targeted spec rather than the full sbt test keeps the loop fast on a large Scala build. Once the last todowrite entry closes, Atlas runs the full ScalaTest via sbt test once to confirm nothing regressed, then runs scalafmt so the fixes land format-clean.

How does Atlas keep Scala test fixes reviewable and reversible?

Atlas computes a unified diff for every file edit and surfaces it for approval before writing, and it snapshots file changes as git patches so edits can be diffed and rolled back. A Scala fix that made 12 specs green by weakening an assertion is caught in review, not in production.

Triage is where an agent is most tempted to make tests pass rather than make code correct. Atlas's review surface is what makes that visible. Every edit to a .scala file under src/main/scala or src/test/scala arrives as a unified diff you approve. Every bash call, including sbt test and scalafmt, is permission-gated against allow, ask, and deny rules before it runs. And because Atlas snapshots file changes as git patches, a fix that turned out to paper over the real cause can be diffed and rolled back rather than untangled by hand. Atlas reads git branches, status, and diffs, and can stage and create commits on your behalf once the suite is genuinely green.

Step by step

01Run atlas in a Scala project with a build.sbt so Atlas can read your traits, implicits, and sbt modules.
02Run ScalaTest via sbt test with the bash tool, passing a generous timeout in milliseconds so a slow sbt compile is not killed mid-run.
03If the output was truncated, read the file named in the ...output truncated... header to see the complete log; bash truncates at 2000 lines or 50 KB.
04Group the failures by root cause with grep over the saved log rather than by ScalaTest spec name, since one broken implicit can redden a dozen specs.
05Record one todowrite entry per distinct cause, with status pending, so the fixes are tracked instead of forgotten.
06Fix the causes one at a time with the edit tool, re-running only the affected ScalaTest specs via sbt test between changes.
07Run the full ScalaTest via sbt test once at the end to confirm nothing regressed across the other sbt modules.
08Run scalafmt on the touched .scala files, review the unified diff Atlas surfaces, then commit.

Frequently asked questions

how to triage a wall of failing ScalaTest specs: Run ScalaTest via sbt test through Atlas's bash tool, then grep the saved log to group failures by root cause rather than by spec name. Atlas records one todowrite entry per distinct cause with status pending, and fixes them one at a time with edit, re-running only the affected specs.
why is my sbt test output truncated in Atlas: The Atlas bash tool truncates displayed output at 2000 lines or 50 KB so a full sbt test run does not flood the model's context. The complete log is written to a retained file and the path is reported in the ...output truncated... header, so read it to see everything.
how do I stop Atlas from killing a slow sbt test run: Pass a generous timeout in milliseconds to the bash tool. A first sbt test often spends minutes in incremental compilation, macro expansion, and implicit resolution before ScalaTest prints anything, and a run killed at that point looks like a failure when it was only slow.
should I group Scala test failures by test name or by cause: By cause. In Scala a single changed implicit in a package object or a modified case class field can redden a dozen specs at once. Atlas greps the saved sbt test log for shared exception types and compiler errors, then records one todowrite entry per distinct root cause.
does Atlas re-run the whole Scala suite after every fix: No. Atlas fixes the causes one at a time with edit and re-runs only the affected ScalaTest specs via sbt test between changes, which keeps the loop fast on a large multi-module build. The full sbt test runs once at the end to confirm nothing regressed.
how do I know an Atlas test fix is real and not just a weakened assertion: Atlas computes a unified diff for every file edit and surfaces it for approval before writing, so every change to a .scala file under src/test/scala is reviewed before it lands. Atlas also snapshots file changes as git patches, so a bad fix can be diffed and rolled back.
atlas Scala sbt setup: Run atlas in a project with a build.sbt. Atlas reads your traits, implicits, and sbt modules, and can refactor to typeclasses or add ScalaTest cases, with the diff reviewed first. Tests run as ScalaTest via sbt test and formatting through scalafmt.
where does Atlas save the full sbt test log: The Atlas bash tool writes the complete log to a retained file and names the path in the truncation header of its output. Read that file to see every ScalaTest failure, including the ones cut off by the 2000 line or 50 KB display limit.

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