mesh-catalog/modules/mesh-delivery-gate/cmd/mesh-delivery-gate/pullkey_test.go

package main

import (
	"errors"
	"sync"
	"testing"
)

// **The pull request's key** (novox/hq ADR 0406 §4, issue 975): one key per pull request on the bus, holding its head,
// the trunk commit its current check is asked against and its verdict, written by compare-and-set. A head the forge
// announces writes head and trunk; a verdict for that head and trunk writes the verdict; nothing else writes.

type fakePulls struct {
	mu     sync.Mutex
	keys   map[string]PullKey
	writes int
	// lose makes the first n writes lose to another writer, which sets rival.
	lose  int
	rival PullKey
}

func newFakePulls() *fakePulls { return &fakePulls{keys: map[string]PullKey{}} }

func (f *fakePulls) Change(key string, apply func(PullKey) (PullKey, bool)) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	for tries := 0; tries < 5; tries++ {
		next, write := apply(f.keys[key])
		if !write {
			return nil
		}
		if f.lose > 0 { // another writer was first: read again and apply again
			f.lose--
			f.keys[key] = f.rival
			continue
		}
		f.keys[key] = next
		f.writes++
		return nil
	}
	return errors.New("lost the race too often")
}

func (f *fakePulls) get(key string) PullKey {
	f.mu.Lock()
	defer f.mu.Unlock()
	return f.keys[key]
}

const appKey = "novox.app.7"

func announcedAt(head, trunk string) PullEvent {
	p := pr("novox/app", 7, head, "feat/x", "src/a.go")
	p.BaseSHA = trunk
	return p
}

func TestAnAnnouncedHeadWritesTheKeyAndTheSameAnnouncementAgainWritesNothing(t *testing.T) {
	w := newWorld(t)
	pulls := newFakePulls()
	w.h.Pulls = pulls
	p := announcedAt(readyHead, "t1t1t1t1t1t1")
	w.h.PullUpdated(p)
	w.h.KeepPull(p)
	if got := pulls.get(appKey); got.Head != readyHead || got.Trunk != "t1t1t1t1t1t1" || got.Verdict != "" {
		t.Fatalf("the key holds %+v", got)
	}
	w.h.KeepPull(p)
	if pulls.writes != 1 {
		t.Fatalf("the same announcement wrote %d times", pulls.writes)
	}
}

func TestANewTrunkCommitClearsTheVerdictAndANewHeadReplacesTheKey(t *testing.T) {
	w := newWorld(t)
	pulls := newFakePulls()
	w.h.Pulls = pulls
	w.h.KeepPull(announcedAt(readyHead, "t1t1t1t1t1t1"))
	w.h.KeepPull(announcedAt(readyHead, "t2t2t2t2t2t2"))
	if got := pulls.get(appKey); got.Trunk != "t2t2t2t2t2t2" || got.Verdict != "" {
		t.Fatalf("the check asked again against a new trunk left %+v", got)
	}
	w.h.KeepPull(announcedAt(pushed, "t2t2t2t2t2t2"))
	if got := pulls.get(appKey); got.Head != pushed {
		t.Fatalf("a new head left %+v", got)
	}
}

func TestAMeshCheckForTheKeysHeadAndTrunkIsWrittenAndOneForAnotherIsNot(t *testing.T) {
	w := newWorld(t)
	pulls := newFakePulls()
	w.h.Pulls = pulls
	w.h.PullUpdated(announcedAt(readyHead, "a1a1a1a1a1a1"))
	w.h.KeepPull(announcedAt(readyHead, "a1a1a1a1a1a1"))
	status := func(head, trunk, state string) ForgeStatusEvent {
		return ForgeStatusEvent{Owner: "novox", Repo: "app", SHA: head, Context: ctxCheck, State: state,
			Description: "pass " + head[:12] + " on " + trunk + " | unit 3 run"}
	}
	w.h.KeepCheckVerdict(status(pushed, "a1a1a1a1a1a1", "success"))
	if pulls.get(appKey).Verdict != "" {
		t.Fatal("a verdict for another head was written")
	}
	w.h.KeepCheckVerdict(status(readyHead, "b2b2b2b2b2b2", "success"))
	if pulls.get(appKey).Verdict != "" {
		t.Fatal("a verdict for another trunk commit was written")
	}
	w.h.KeepCheckVerdict(status(readyHead, "a1a1a1a1a1a1", "pending"))
	if pulls.get(appKey).Verdict != "" {
		t.Fatal("a pending check was written as a verdict")
	}
	w.h.KeepCheckVerdict(status(readyHead, "a1a1a1a1a1a1", "success"))
	if got := pulls.get(appKey); got.Verdict != "pass" {
		t.Fatalf("the key holds %+v", got)
	}
}

func TestALostRaceReadsTheKeyAgainAndAppliesTheChangeToWhatItFound(t *testing.T) {
	w := newWorld(t)
	pulls := newFakePulls()
	pulls.lose, pulls.rival = 1, PullKey{Head: readyHead, Trunk: "t1t1t1t1t1t1", Verdict: "pass"}
	w.h.Pulls = pulls
	// The rival writer already holds this very head and trunk with a verdict: the change finds nothing to write.
	w.h.KeepPull(announcedAt(readyHead, "t1t1t1t1t1t1"))
	if got := pulls.get(appKey); got.Verdict != "pass" || pulls.writes != 0 {
		t.Fatalf("after the lost race the key holds %+v after %d writes", got, pulls.writes)
	}
}

// The forge's catch-up after a restart can announce a merge again past the bus's de-duplication window (issue 975):
// heard again, it changes nothing, and moves no trunk back.
func TestTheSameMergeHeardAgainAfterALaterMergeMovesNoTrunkBack(t *testing.T) {
	w := newWorld(t)
	a, b := "aaaaaaaaaaaaaaaa", "bbbbbbbbbbbbbbbb"
	w.h.PullUpdated(pr("novox/app", 7, readyHead, "feat/x", "src/a.go"))
	w.h.PullUpdated(pr("novox/app", 8, a, "feat/y", "src/a.go"))
	w.h.PullUpdated(pr("novox/app", 9, b, "feat/z", "src/a.go"))
	w.h.Checked(judgedAt("novox/app", 7, readyHead, "pass", "m8m8m8m8m8m8"))
	w.h.PullMerged(merged("novox/app", 8, a, "m8m8m8m8m8m8"))
	w.h.PullMerged(merged("novox/app", 9, b, "m9m9m9m9m9m9"))
	id := IDOf("novox/app", readyHead)
	before := w.delivery(id)
	w.h.PullMerged(merged("novox/app", 8, a, "m8m8m8m8m8m8")) // announced again, past the window
	after := w.delivery(id)
	if after.TrunkNow != before.TrunkNow || after.TrunkNow != "m9m9m9m9m9m9" {
		t.Fatalf("the trunk moved from %q to %q on a merge heard again; wanted it to stay m9m9m9m9m9m9", before.TrunkNow, after.TrunkNow)
	}
}

// The forge's mesh/check event handled wholly between the announcement's PullUpdated and its KeepPull (the two events are
// taken on goroutines of their own): the verdict must still reach the pull request's key.
func TestAVerdictHeardBeforeTheKeyIsWrittenReachesTheKey(t *testing.T) {
	w := newWorld(t)
	pulls := newFakePulls()
	w.h.Pulls = pulls
	p := announcedAt(readyHead, "a1a1a1a1a1a1")
	w.h.PullUpdated(p)
	s := ForgeStatusEvent{Owner: "novox", Repo: "app", SHA: readyHead, Context: ctxCheck, State: "success",
		Description: "pass " + readyHead[:12] + " on a1a1a1a1a1a1 | unit 3 run"}
	w.h.CommitStatus(s)
	w.h.KeepCheckVerdict(s)
	w.h.KeepPull(p)
	if got := pulls.get(appKey); got.Head != readyHead || got.Verdict != "pass" {
		t.Fatalf("the key holds %+v, want the head with the verdict pass", got)
	}
}