appBehaviorReporter.ts

import { writeFile } from "node:fs/promises";
import type { TestModule } from "vitest/node";
import type { Reporter } from "vitest/reporters";

const outputPath = "APP_BEHAVIOR.md";

export default class AppBehaviorReporter implements Reporter {
  async onTestRunEnd(testModules: readonly TestModule[]) {
    // The doc is committed from local runs, so there's no reason for a build server to regenerate it.
    if (process.env.CI) return;

    const rootGroup: SummaryGroup = { children: new Map(), tests: [] };

    for (const testModule of testModules) {
      for (const testCase of testModule.children.allTests()) {
        const parts = testCase.fullName.split(" > ");
        // Skip top-level tests that aren't inside a describe block.
        if (parts.length === 1) continue;
        addTest(rootGroup, parts);
      }
    }

    const lines = ["<!-- Autogenerated by appBehaviorReporter.ts -->", "# App Behavior", ""];
    appendGroupLines(lines, rootGroup, 0);
    await writeFile(outputPath, `${lines.join("\n").trimEnd()}\n`);
  }
}

type SummaryGroup = {
  children: Map<string, SummaryGroup>;
  tests: string[];
};

function addTest(group: SummaryGroup, parts: string[]) {
  if (parts.length === 1) {
    group.tests.push(parts[0]);
    return;
  }

  const [describeName, ...remainingParts] = parts;
  const childGroup = group.children.get(describeName) ?? { children: new Map(), tests: [] };
  group.children.set(describeName, childGroup);
  addTest(childGroup, remainingParts);
}

function appendGroupLines(lines: string[], group: SummaryGroup, depth: number) {
  const indent = "  ".repeat(depth);
  for (const test of group.tests) {
    lines.push(`${indent}- ${test}`);
  }
  for (const [name, childGroup] of group.children) {
    lines.push(`${indent}- ${name}`);
    appendGroupLines(lines, childGroup, depth + 1);
  }
}