Keep make test under 2 GB of memory (closes #344)

Every test that starts a database hashed the bootstrap admin password
with Argon2id at 64 MB, which under -race holds about 150 MB per hash,
across dozens of parallel tests. The test packages that hash now lower
the memory cost to 1 MB from TestMain. One test still hashes and
verifies at the shipped parameters, which are unchanged.

script/test also runs at most four packages and eight parallel tests
at once: unbounded, a many-core host linked and ran every test binary
together.

Model: opus-5-5

internal/database/export_test.go

@@ -79,3 +79,9 @@ func (d *Database) ExportSetBannerOut(w io.Writer) {
 func DummyPasswordHashForTest() string {
 	return dummyPasswordHash()
 }
+
+// HashPasswordWithDefaultsForTest hashes with the shipped Argon2id
+// parameters, which TestMain has lowered for HashPassword itself.
+func HashPasswordWithDefaultsForTest(password string) (string, error) {
+	return hashPasswordWith(password, DefaultPasswordConfig())
+}

internal/database/main_test.go

@@ -0,0 +1,14 @@
+package database_test
+
+import (
+	"testing"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// TestMain lowers the password hashing cost before any test runs. See
+// database.LowerPasswordHashCostForTest.
+func TestMain(m *testing.M) {
+	database.LowerPasswordHashCostForTest()
+	m.Run()
+}

internal/database/password.go

@@ -63,10 +63,24 @@ func DefaultPasswordConfig() *PasswordConfig {
 	}
 }
 
+// hashConfig is what HashPassword hashes with: the defaults above.
+// Only a test binary changes it, through LowerPasswordHashCostForTest,
+// before any test runs.
+//
+//nolint:gochecknoglobals // see above
+var hashConfig = DefaultPasswordConfig()
+
 // HashPassword generates an Argon2id hash of the password
 func HashPassword(password string) (string, error) {
-	config := DefaultPasswordConfig()
+	return hashPasswordWith(password, hashConfig)
+}
 
+// hashPasswordWith generates an Argon2id hash of the password with
+// the given parameters.
+func hashPasswordWith(
+	password string,
+	config *PasswordConfig,
+) (string, error) {
 	// Generate a salt
 	salt := make([]byte, config.SaltLen)
 

internal/database/password_test.go

@@ -192,6 +192,36 @@ func TestHashPasswordUniqueness(t *testing.T) {
 	}
 }
 
+// TestHashPassword_ShippedParameters hashes and verifies at the
+// shipped Argon2id parameters. Every other test hashes at the lowered
+// memory cost TestMain sets, so this is the one that keeps production
+// hashing covered. One hash and one verification: each costs 64 MB.
+func TestHashPassword_ShippedParameters(t *testing.T) {
+	t.Parallel()
+
+	password := "correct horse battery staple"
+
+	hash, err := database.HashPasswordWithDefaultsForTest(password)
+	if err != nil {
+		t.Fatalf("hashing with the shipped parameters: %v", err)
+	}
+
+	const shipped = "$argon2id$v=19$m=65536,t=1,p=4$"
+
+	if !strings.HasPrefix(hash, shipped) {
+		t.Errorf("hash = %q, want prefix %q", hash, shipped)
+	}
+
+	valid, err := database.VerifyPassword(password, hash)
+	if err != nil {
+		t.Fatalf("VerifyPassword() error = %v", err)
+	}
+
+	if !valid {
+		t.Error("VerifyPassword() returned false for correct password")
+	}
+}
+
 // TestVerifyDummyPassword_DoesRealWork covers the anti-enumeration
 // path. Login charges an unknown username a verification against a
 // dummy hash so that a nonexistent account is not answered in

internal/database/testing.go

@@ -45,3 +45,20 @@ func NewTestWebhookDBManagerWithLogger(
 		log:     log,
 	}
 }
+
+// testArgon2Memory is the Argon2id memory cost, in KiB, that test
+// binaries hash with: 1 MB instead of the shipped 64 MB.
+const testArgon2Memory = 1024
+
+// LowerPasswordHashCostForTest makes HashPassword use a 1 MB Argon2id
+// memory cost instead of the shipped 64 MB, for the rest of the
+// process. Call it from TestMain, before any test runs.
+//
+// Every test that starts a database hashes the bootstrap admin
+// password, and a package runs dozens of those tests in parallel.
+// Under the race detector each 64 MB hash holds about 150 MB resident.
+// VerifyPassword reads the cost from the hash it checks, so
+// verification follows. Production code never calls this.
+func LowerPasswordHashCostForTest() {
+	hashConfig.Memory = testArgon2Memory
+}

internal/gormlog/main_test.go

@@ -0,0 +1,14 @@
+package gormlog_test
+
+import (
+	"testing"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// TestMain lowers the password hashing cost before any test runs. See
+// database.LowerPasswordHashCostForTest.
+func TestMain(m *testing.M) {
+	database.LowerPasswordHashCostForTest()
+	m.Run()
+}

internal/handlers/main_test.go

@@ -0,0 +1,14 @@
+package handlers_test
+
+import (
+	"testing"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// TestMain lowers the password hashing cost before any test runs. See
+// database.LowerPasswordHashCostForTest.
+func TestMain(m *testing.M) {
+	database.LowerPasswordHashCostForTest()
+	m.Run()
+}

internal/resetpw/main_test.go

@@ -0,0 +1,14 @@
+package resetpw_test
+
+import (
+	"testing"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// TestMain lowers the password hashing cost before any test runs. See
+// database.LowerPasswordHashCostForTest.
+func TestMain(m *testing.M) {
+	database.LowerPasswordHashCostForTest()
+	m.Run()
+}

internal/resetpw/resetpw_test.go

@@ -140,7 +140,7 @@ func (n *noopEvictor) EvictWebhook(string) {}
 // and the database, exactly as internal/handlers builds them.
 //
 // One application per test function, not per case: every start that
-// finds no account seeds one at 64 MB of Argon2id, and this package's
+// finds no account seeds one with an Argon2id hash, and this package's
 // budget is not the place to spend that repeatedly.
 func newServerApp(
 	t *testing.T, dir string,

internal/server/main_test.go

@@ -0,0 +1,14 @@
+package server_test
+
+import (
+	"testing"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// TestMain lowers the password hashing cost before any test runs. See
+// database.LowerPasswordHashCostForTest.
+func TestMain(m *testing.M) {
+	database.LowerPasswordHashCostForTest()
+	m.Run()
+}

script/test

@@ -22,13 +22,18 @@
 # The one figure above 90s is GOMAXPROCS 1, a synthetic core floor rather than
 # a condition CI runs under. If a CPU-limited runner ever puts a real run near
 # 67s, that is the datum to revisit the org figure with.
+#
+# -p 4 -parallel 8 keep the run under 2 GB of memory: at most four test
+# binaries build or run at once, each with at most eight parallel tests. Under
+# -race every test binary and every link costs a few hundred MB, so the
+# defaults (one per core) add up to several GB on a many-core host.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    go test -v -race -timeout 90s ./...
+    go test -v -race -p 4 -parallel 8 -timeout 90s ./...
 }
 
 main "$@"