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fix(test): StdioMcpTransport process tests — race against fast child … #46

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Merged
Skobeltsyn merged 1 commit into from
May 5, 2026
Merged

fix(test): StdioMcpTransport process tests — race against fast child … #46

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13 changes: 8 additions & 5 deletions src/test/kotlin/agents_engine/mcp/StdioMcpTransportForProcessTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -44,12 +44,15 @@ class StdioMcpTransportForProcessTest {
fun `forProcess applies env map to the child process`() {
// Child reads $TEST_VAR via shell, formats a JSON-RPC response with the
// value, then exits. If env wasn't applied, $TEST_VAR is empty.
// `read req` makes the child block on stdin so rpc()'s write lands in
// the pipe before the child exits — without this, fast process startup
// (Linux CI) can race the write against the child's exit and produce a
// BrokenPipe IOException. See discussion in the PR for #1018 — flake
// surfaced once Gradle 9.5 sped up CI scheduling.
val transport = forProcess(
command = listOf("sh", "-c", "printf '{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":\"%s\"}\\n' \"\$TEST_VAR\""),
command = listOf("sh", "-c", "read req; printf '{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":\"%s\"}\\n' \"\$TEST_VAR\""),
env = mapOf("TEST_VAR" to "applied"),
)
// We don't write a request — the child writes the response unprompted
// and exits. rpc() with id=1 will read the line.
val response = transport.rpc("""{"jsonrpc":"2.0","id":1,"method":"x"}""")
assertTrue(response.contains("\"result\":\"applied\""), "env var not applied; got: $response")
}
Expand All @@ -58,7 +61,7 @@ class StdioMcpTransportForProcessTest {
fun `forProcess applies workingDir to the child process`() {
val tmp = File(System.getProperty("java.io.tmpdir"))
val transport = forProcess(
command = listOf("sh", "-c", "printf '{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":\"%s\"}\\n' \"\$(pwd)\""),
command = listOf("sh", "-c", "read req; printf '{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":\"%s\"}\\n' \"\$(pwd)\""),
workingDir = tmp,
)
val response = transport.rpc("""{"jsonrpc":"2.0","id":1,"method":"x"}""")
Expand All @@ -77,7 +80,7 @@ class StdioMcpTransportForProcessTest {
val transport = forProcess(
command = listOf(
"sh", "-c",
"""echo err-line-1 >&2; echo err-line-2 >&2; printf '{"jsonrpc":"2.0","id":1,"result":null}\n'""",
"""read req; echo err-line-1 >&2; echo err-line-2 >&2; printf '{"jsonrpc":"2.0","id":1,"result":null}\n'""",
),
stderrSink = { received.add(it) },
)
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