Update env tests

packages/babel-preset-env/test/top-level-await.js

@@ -0,0 +1,42 @@
+import env from "..";
+import * as babel from "@babel/core";
+
+describe("supportsTopLevelAwait enables the parser plugin for old parser versions", () => {
+  function extractParserOptions(api, { ref }) {
+    return {
+      manipulateOptions(opts, parserOpts) {
+        ref.parserOpts = parserOpts;
+      },
+      visitor: {},
+    };
+  }
+
+  it("supported", () => {
+    const ref = {};
+    babel.transformSync("", {
+      configFile: false,
+      presets: [env],
+      plugins: [[extractParserOptions, { ref }]],
+      caller: {
+        name: "test",
+        supportsTopLevelAwait: true,
+      },
+    });
+
+    expect(ref.parserOpts.plugins).toContain("topLevelAwait");
+  });
+
+  it("unsupported", () => {
+    const ref = {};
+    babel.transformSync("", {
+      configFile: false,
+      presets: [env],
+      plugins: [[extractParserOptions, { ref }]],
+      caller: {
+        name: "test",
+      },
+    });
+
+    expect(ref.parserOpts.plugins).not.toContain("topLevelAwait");
+  });
+});