fix(agent/agentcontainers): fix `TestDevcontainerDiscovery/AutoStart` flake #19179

DanielleMaywood · 2025-08-05T12:05:32Z

… flake Fixes coder/internal#864 I've ripped out the mock infrastructure for this test, and have instead replaced it with our `fakeContainerCLI` and `fakeDevcontainerCLI` utilities.

DanielleMaywood · 2025-08-05T12:28:46Z

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coderabbitai · 2025-08-05T12:28:53Z

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Pull Request Overview

This PR fixes a flaky test TestDevcontainerDiscovery/AutoStart by replacing gomock-based mocking with a deterministic fake implementation. The test was likely flaking due to race conditions or timing issues with mock expectations.

Key changes:

Replace gomock mocking with a deterministic fake devcontainer CLI implementation
Add explicit tracking of Up method calls to verify expected behavior
Simplify test structure by using data-driven configuration maps instead of complex mock setups

Comments suppressed due to low confidence (1)

agent/agentcontainers/api_test.go:773

The assertion should use assert.Equal instead of require.Equal since this is inside a loop and a failure here should not prevent checking other configurations. Using require.Equal will stop the test immediately on first failure.

					require.ErrorContains(t, got, tc.expectedErr, "want error")

agent/agentcontainers/api_test.go

coderabbitai · 2025-08-05T12:36:45Z

📝 Walkthrough

Walkthrough

The TestDevcontainerDiscovery test in agent/agentcontainers/api_test.go was refactored and enhanced to robustly verify the auto-start behavior of devcontainers. The test infrastructure now uses a configurable fake CLI implementation, enabling dynamic configuration and tracking of which devcontainers are started based on their AutoStart setting. The test covers multiple auto-start scenarios and asserts correct behavior.

Changes

Cohort / File(s)	Change Summary
Devcontainer Discovery Test Refactor `agent/agentcontainers/api_test.go`	Refactored `TestDevcontainerDiscovery` to use a custom `fakeDevcontainerCLI` with dynamic config and `Up` tracking. Added/updated subtests for various auto-start scenarios. Modified method signatures and struct fields to support new test logic. Removed gomock usage in favor of internal call tracking.

Sequence Diagram(s)

sequenceDiagram
    participant Test
    participant FakeDevcontainerCLI
    participant API

    Test->>FakeDevcontainerCLI: Set up configMap and up function
    Test->>API: Start API with FakeDevcontainerCLI
    API->>FakeDevcontainerCLI: ReadConfig(configPath)
    FakeDevcontainerCLI-->>API: Return DevcontainerConfig (with AutoStart)
    API->>FakeDevcontainerCLI: Up(workspaceFolder, configPath) [if AutoStart]
    FakeDevcontainerCLI-->>API: Record Up call
    Test->>API: Wait for discovery and Up calls
    Test->>Test: Assert correct Up invocations and devcontainer count
    Test->>API: Close API

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~15 minutes

Assessment against linked issues

Objective	Addressed	Explanation
Ensure `TestDevcontainerDiscovery/AutoStart/MultipleEnabled` reliably verifies multiple enabled devcontainers auto-start (#864)	✅
Remove reliance on gomock for Up calls in devcontainer discovery tests (#864)	✅
Track and assert correct Up invocations for devcontainers with AutoStart enabled (#864)	✅

Assessment against linked issues: Out-of-scope changes

No out-of-scope changes were found.

Note

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📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 8b66a5a and 72514f8.

📒 Files selected for processing (1)

agent/agentcontainers/api_test.go (5 hunks)

🔇 Additional comments (4)

agent/agentcontainers/api_test.go (4)

74-85: Good refactoring to improve test flexibility.

The addition of the up function field and configMap enables dynamic behavior in tests, making it easier to verify which devcontainers are started based on their configuration. This is a cleaner approach than using mocks for this use case.

87-102: Proper implementation of configurable Up behavior.

The method correctly delegates to the custom up function when provided, while maintaining backward compatibility with the channel-based approach for existing tests.

118-135: Excellent implementation of path-specific configuration.

The ReadConfig method now properly supports returning different configurations based on the config path, which is crucial for testing multiple devcontainers with varying AutoStart settings.

3583-3846: Excellent refactoring of the AutoStart test to address flakiness.

The test has been significantly improved:

Replaced gomock expectations with a deterministic fake implementation that tracks Up calls

Added comprehensive test scenarios covering different AutoStart configurations

Uses proper synchronization with mutex to track concurrent operations

Verifies both the discovery of devcontainers and that Up is called only for those with AutoStart: true

This approach should resolve the flaky test issue by providing better control over the test execution flow and eliminating timing dependencies.

✨ Finishing Touches

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Post copyable unit tests in a comment
Commit unit tests in branch danielle/fix-devcontainer-flake

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mafredri

LGTM 👍🏻

johnstcn

Some (belated) comments below, but nothing blocking.

johnstcn · 2025-08-05T14:38:24Z

agent/agentcontainers/api_test.go

+					autoStart := config.Configuration.Customizations.Coder.AutoStart
+					wasUpCalled := upCalledFor[configPath]
+
+					require.Equal(t, autoStart, wasUpCalled)


Suggest assert here instead.

johnstcn · 2025-08-05T14:38:56Z

agent/agentcontainers/api_test.go

+				// And: `up` was called on the correct containers
+				for configPath, config := range tt.configMap {
+					autoStart := config.Configuration.Customizations.Coder.AutoStart
+					wasUpCalled := upCalledFor[configPath]


Will this handle the case where we call up for something not in config.Configuration.Customizations.Coder.AutoStart?

fix(agent/agentcontainers): fix TestDevcontainerDiscovery/AutoStart…

713211b

… flake Fixes coder/internal#864 I've ripped out the mock infrastructure for this test, and have instead replaced it with our `fakeContainerCLI` and `fakeDevcontainerCLI` utilities.

github-actions bot assigned DanielleMaywood Aug 5, 2025

chore: apply make fmt

72514f8

DanielleMaywood marked this pull request as ready for review August 5, 2025 12:28

DanielleMaywood requested a review from Copilot August 5, 2025 12:28

Copilot AI reviewed Aug 5, 2025

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DanielleMaywood requested review from mafredri and johnstcn August 5, 2025 12:41

mafredri approved these changes Aug 5, 2025

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DanielleMaywood merged commit 760dc8b into main Aug 5, 2025
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DanielleMaywood deleted the danielle/fix-devcontainer-flake branch August 5, 2025 12:58

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johnstcn reviewed Aug 5, 2025

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fix(agent/agentcontainers): fix `TestDevcontainerDiscovery/AutoStart` flake #19179

fix(agent/agentcontainers): fix `TestDevcontainerDiscovery/AutoStart` flake #19179

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fix(agent/agentcontainers): fix TestDevcontainerDiscovery/AutoStart flake #19179

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fix(agent/agentcontainers): fix `TestDevcontainerDiscovery/AutoStart` flake #19179

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