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test: fix two flaky tests (darwin start_time regex, memstats HeapReleased drift) #2050

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Merged
bwplotka merged 2 commits into from
Jul 8, 2026
+11 −6
Merged

test: fix two flaky tests (darwin start_time regex, memstats HeapReleased drift) #2050

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6cdc504
test(process_collector): match scientific-notation start time on darwin
kakkoyun Jul 8, 2026
dd9aa65
test(collector): stabilize TestMemStatsEquivalence against HeapReleas…
kakkoyun Jul 8, 2026
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13 changes: 9 additions & 4 deletions prometheus/go_collector_latest_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ import (
"reflect"
"regexp"
"runtime"
"runtime/debug"
"runtime/metrics"
"strings"
"sync"
Expand Down Expand Up @@ -270,12 +271,16 @@ func TestMemStatsEquivalence(t *testing.T) {
samplesMap[descs[i].Name] = &samples[i]
}

// Force a GC cycle to try to reach a clean slate.
runtime.GC()
// Reach a stable slate and hold it for a single measurement window.
// FreeOSMemory runs a GC and returns freed memory to the OS, leaving the
// background scavenger nothing to release; disabling GC for the window
// keeps msReal and msFake observing the same runtime state. Without this,
// HeapReleased could drift between the two reads and fail the comparison.
debug.FreeOSMemory()
defer debug.SetGCPercent(debug.SetGCPercent(-1))

// Populate msReal.
// Populate msReal, then msFake back-to-back within the frozen window.
runtime.ReadMemStats(&msReal)
// Populate msFake and hope that no GC happened in between (:
metrics.Read(samples)

memStatsFromRM(&msFake, samplesMap)
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4 changes: 2 additions & 2 deletions prometheus/process_collector_darwin_test.go
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Expand Up @@ -55,12 +55,12 @@ func TestDarwinProcessCollector(t *testing.T) {
regexp.MustCompile("\nprocess_max_fds [1-9]"),
regexp.MustCompile("\nprocess_open_fds [1-9]"),
regexp.MustCompile("\nprocess_virtual_memory_max_bytes (-1|[1-9])"),
regexp.MustCompile("\nprocess_start_time_seconds [0-9.]{10,}"),
regexp.MustCompile("\nprocess_start_time_seconds [0-9]"),
regexp.MustCompile("\nfoobar_process_cpu_seconds_total [0-9]"),
regexp.MustCompile("\nfoobar_process_max_fds [1-9]"),
regexp.MustCompile("\nfoobar_process_open_fds [1-9]"),
regexp.MustCompile("\nfoobar_process_virtual_memory_max_bytes (-1|[1-9])"),
regexp.MustCompile("\nfoobar_process_start_time_seconds [0-9.]{10,}"),
regexp.MustCompile("\nfoobar_process_start_time_seconds [0-9]"),
} {
if !re.Match(buf.Bytes()) {
t.Errorf("want body to match %s\n%s", re, buf.String())
Expand Down
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