fix: do not echo RemoteTestRunner control frames to test output

[wenytang-ms]

Problem

When running JUnit tests, the Test Results output channel is filled with the Eclipse RemoteTestRunner machine protocol instead of readable output, e.g.:

%TSTTREE2,com.example.FooTest,true,1,false,-1,FooTest,,
%TESTS1,fooBar(com.example.FooTest)
%FAILED1,fooBar(com.example.FooTest)
%TRACES
java.lang.AssertionError: expected:<1> but was:<2>
%TRACEE
%TESTE1,fooBar(com.example.FooTest)
%RUNTIME20

These %-prefixed lines are the wire protocol between the test runner and the extension. They are already parsed by processData() to build the test tree, status, diff messages, and failure details, so echoing them verbatim to the user-facing output is pure noise and breaks parity with the CLI (mvn test / gradle test).

Root cause

JUnitRunnerResultAnalyzer.analyzeData() forwarded every received line to testRun.appendOutput(), without distinguishing protocol frames/payload from user-visible output:

for (const line of lines) {
    this.processData(line);
    this.testContext.testRun.appendOutput(line + '\r\n'); // echoes protocol frames and payload too
}

This was introduced when the analyzer was migrated to the VS Code test API.

Fix

Filter known Eclipse RemoteTestRunner protocol frame prefixes and their protocol payload blocks before appending to the Test Results output channel. This intentionally uses a known-prefix list instead of a broad %[A-Z] regex so legitimate user output such as %OK, %ABC, or %STATUS 200 remains visible.

The filtered prefixes include frames handled by processData() plus runner markers not represented in MessageId, such as %TESTC, %RUNTIME, %MENTER, and %MEXIT.

Expected/actual and trace payloads between %EXPECTS/%EXPECTE, %ACTUALS/%ACTUALE, and %TRACES/%TRACEE are also filtered from raw output because processData() already uses them to populate VS Code's test failure messages, diffs, and stack traces.

Genuine program output (System.out/System.err) is still forwarded if it is present in the runner stream. The analyzer also skips only the final empty split segment produced by a newline-terminated runner chunk, avoiding spurious blank lines while preserving real blank output lines inside a chunk.

Test

Added a regression test asserting that:

• protocol frames do not reach appendOutput, including bare delimiters (%TRACES, %TRACEE, %EXPECTS, %ACTUALS) and numeric frames (%RUNTIME20);
• expected/actual and trace protocol payloads are consumed for UI failure messages but not echoed as raw output;
• real program output (Hello from System.out) is still forwarded;
• percent-prefixed program output (%OK, %ABC, %STATUS 200) is still forwarded;
• a trailing newline on a runner chunk does not append an extra blank output line.

Verified locally with:

npm run compile
npm run lint
npm test

[Copilot]

Pull request overview

This PR reduces noise in the VS Code Test Results output channel by preventing Eclipse RemoteTestRunner protocol/control frames from being echoed as user-facing output, while still allowing real program output and relevant payload lines (e.g., stack traces) through.

Changes:

• Filter %... RemoteTestRunner control frames out of testRun.appendOutput() in JUnitRunnerResultAnalyzer.analyzeData().
• Add a regression test ensuring control frames are not forwarded, but program output and stack-trace content are.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
test/suite/JUnitAnalyzer.test.ts	Adds a regression test to ensure RemoteTestRunner control frames don’t leak into the output channel.
src/runners/junitRunner/JUnitRunnerResultAnalyzer.ts	Stops echoing RemoteTestRunner control frames to the output channel by filtering them during analysis.

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.