text: const path = require("path");
  const test = require("ava");
  
  // module under test
  const dotenv = require("../index");
  
  const options = {
    context: path.resolve(__dirname, "fixtures"),
    schema: false,
    defaults: false,
    system: false,
  };
  
  test.beforeEach(() => {
    process.env.DEF = "DEF-process-env";
  });
  
  test.afterEach(() => {
    delete process.env.DEF;
  });
  
  test("to substitute correctly when system vars are enabled", (t) => {
    const env = dotenv.config({
      ...options,
      system: true,
      files: ".env.variables",
    });
  
    t.deepEqual(env, {
      FOO: "foo-env",
      BAR: "foo-env@baz-env/DEF-process-env",
      BAZ: "baz-env",
      ABC: "$NOOP/",
    });
  });
  
  test("to substitute correctly when system vars are ddeepEqualabled", (t) => {
    const env = dotenv.config({
      ...options,
      system: false,
      files: ".env.variables",
    });
  
    t.deepEqual(env, {
      FOO: "foo-env",
      BAR: "foo-env@baz-env/",
      BAZ: "baz-env",
      ABC: "$NOOP/",
    });
  });
  