test(migration): pin the 0107 review_check_mode backfill against a real pre-migration row (#2852)

The existing reviewCheckMode tests only exercise the application layer
through createTestEnv(), which applies every migration (including 0107)
up front against an empty table -- so the migration's own UPDATE
backfill never ran against a real pre-existing row and could drift
silently.

Mirrors migration-0102-linked-issue-gate-mode.test.ts's approach:
replay every migration before 0107 into a fresh in-memory DB, insert a
raw gate_check_mode='enabled' row exactly as a pre-existing installed
repo would have it, then apply migration 0107 for real and assert the
backfill. Also covers the 'off' and unrecognized-legacy-value cases
failing closed to the new column's 'disabled' default, and a
multi-row backfill in one run.

Author: JSONbored

test/unit/migration-0107-review-check-mode.test.ts

@@ -0,0 +1,81 @@
+import { readFileSync, readdirSync } from "node:fs";
+import { DatabaseSync } from "node:sqlite";
+import { describe, expect, it } from "vitest";
+
+const MIGRATION_FILE = "0107_repository_review_check_mode.sql";
+
+// Replays every migrations/*.sql file BEFORE 0107 into a fresh in-memory DB (mirrors
+// migration-0102-linked-issue-gate-mode.test.ts's own approach), so the table shape this test inserts into is
+// exactly what migration 0107 itself was written against. The TestD1Database helper (test/helpers/d1.ts) can't
+// be reused here: it concatenates and applies EVERY migration (including 0107) up front, so the new
+// review_check_mode column would already be backfilled by the time a test could insert a pre-migration
+// gate_check_mode='enabled' row -- there would be nothing left for 0107's UPDATE to actually backfill.
+function applyMigrationsBefore(cutoffFile: string): DatabaseSync {
+  const db = new DatabaseSync(":memory:");
+  const files = readdirSync("migrations")
+    .filter((file) => file.endsWith(".sql") && file < cutoffFile)
+    .sort();
+  for (const file of files) db.exec(readFileSync(`migrations/${file}`, "utf8"));
+  return db;
+}
+
+function applyMigration(db: DatabaseSync, file: string): void {
+  db.exec(readFileSync(`migrations/${file}`, "utf8"));
+}
+
+function insertRepositorySettingsRow(db: DatabaseSync, repoFullName: string, gateCheckMode: string): void {
+  db.prepare("INSERT INTO repository_settings (repo_full_name, gate_check_mode) VALUES (?, ?)").run(repoFullName, gateCheckMode);
+}
+
+function readReviewCheckMode(db: DatabaseSync, repoFullName: string): string {
+  const row = db.prepare("SELECT review_check_mode FROM repository_settings WHERE repo_full_name = ?").get(repoFullName) as
+    | { review_check_mode: string }
+    | undefined;
+  if (!row) throw new Error(`no repository_settings row for ${repoFullName}`);
+  return row.review_check_mode;
+}
+
+describe("migration 0107: review_check_mode backfill (#2852)", () => {
+  it("backfills a pre-existing gate_check_mode='enabled' row to review_check_mode='required', via the real migration", () => {
+    const db = applyMigrationsBefore(MIGRATION_FILE);
+    insertRepositorySettingsRow(db, "acme/legacy-enabled", "enabled");
+
+    applyMigration(db, MIGRATION_FILE);
+
+    expect(readReviewCheckMode(db, "acme/legacy-enabled")).toBe("required");
+  });
+
+  it("leaves a pre-existing gate_check_mode='off' row on the new column's default 'disabled'", () => {
+    const db = applyMigrationsBefore(MIGRATION_FILE);
+    insertRepositorySettingsRow(db, "acme/legacy-off", "off");
+
+    applyMigration(db, MIGRATION_FILE);
+
+    expect(readReviewCheckMode(db, "acme/legacy-off")).toBe("disabled");
+  });
+
+  // The backfill's WHERE clause is an exact match on 'enabled' -- any other legacy/unrecognized value (not
+  // just the documented 'off') must fail closed to the new column's 'disabled' default rather than publish
+  // the check-run for a repo that never explicitly opted in.
+  it("leaves a row with an unrecognized legacy gate_check_mode value on the new column's default 'disabled'", () => {
+    const db = applyMigrationsBefore(MIGRATION_FILE);
+    insertRepositorySettingsRow(db, "acme/legacy-weird", "weird-legacy-value");
+
+    applyMigration(db, MIGRATION_FILE);
+
+    expect(readReviewCheckMode(db, "acme/legacy-weird")).toBe("disabled");
+  });
+
+  it("backfills multiple pre-existing rows independently in one migration run", () => {
+    const db = applyMigrationsBefore(MIGRATION_FILE);
+    insertRepositorySettingsRow(db, "acme/legacy-enabled-1", "enabled");
+    insertRepositorySettingsRow(db, "acme/legacy-enabled-2", "enabled");
+    insertRepositorySettingsRow(db, "acme/legacy-off-1", "off");
+
+    applyMigration(db, MIGRATION_FILE);
+
+    expect(readReviewCheckMode(db, "acme/legacy-enabled-1")).toBe("required");
+    expect(readReviewCheckMode(db, "acme/legacy-enabled-2")).toBe("required");
+    expect(readReviewCheckMode(db, "acme/legacy-off-1")).toBe("disabled");
+  });
+});