test: the popup boot in the jest suite sends no request to the internet (closes #559)

bootPopup() in tests/support/popupBoot.js mocked three of the modules
that reach the network, but a boot onto the transaction screen still
asked Blockscout for its transaction, and a boot onto the confirmation
screen had src/shared/etherscanLabels.js look the recipient up on
Etherscan, both through the real fetch().
tests/persistedFieldContract.test.js boots onto both, so every run sent
those requests and logged their answers after its tests had finished.
bootPopup() now replaces fetch() with the throwing stub the rest of the
suite uses, and cleanupPopup() puts it back. tests/popupBoot.test.js
checks that both requests reach the stub.

Model: opus-5-5

tests/popupBoot.test.js

@@ -9,6 +9,7 @@ const {
     bootPopup,
     cleanupPopup,
     unversionedValidProfile,
+    ADDRESS,
 } = require("./support/popupBoot");
 
 const FLASH_MS = 10;
@@ -40,3 +41,47 @@ test("a flash message's timer does not fire after cleanupPopup()", async () => {
 
     await wait(FLASH_MS * 5);
 });
+
+// A boot onto a screen whose requests no mocked module answers: they reach the
+// boot's fetch() stub, never the internet
+// (https://git.eeqj.de/sneak/AutistMask/issues/559).
+function restoringOnto(view, viewData) {
+    return unversionedValidProfile({
+        currentView: view,
+        selectedWallet: 0,
+        selectedAddress: 0,
+        viewStack: ["main"],
+        viewData,
+    });
+}
+
+test("the transaction screen's Blockscout request reaches the stub", async () => {
+    const page = await bootPopup(
+        restoringOnto("transaction", {
+            tx: { hash: "0x1", from: ADDRESS, to: ADDRESS },
+        }),
+    );
+
+    expect(page.visibleViews()).toEqual(["transaction"]);
+    expect(globalThis.fetch.mock.calls.map((call) => call[0])).toEqual([
+        "https://eth.blockscout.com/api/v2/transactions/0x1",
+    ]);
+});
+
+test("the confirmation screen's Etherscan lookup reaches the stub", async () => {
+    const page = await bootPopup(
+        restoringOnto("confirm-tx", {
+            pendingTx: {
+                token: "ETH",
+                from: ADDRESS,
+                to: ADDRESS,
+                amount: "1",
+            },
+        }),
+    );
+
+    expect(page.visibleViews()).toEqual(["confirm-tx"]);
+    expect(globalThis.fetch.mock.calls.map((call) => call[0])).toEqual([
+        "https://etherscan.io/address/" + ADDRESS,
+    ]);
+});

tests/support/popupBoot.js

@@ -45,6 +45,7 @@ const realSetInterval = globalThis.setInterval;
 const realClearInterval = globalThis.clearInterval;
 const realSetTimeout = globalThis.setTimeout;
 const realClearTimeout = globalThis.clearTimeout;
+const realFetch = globalThis.fetch;
 
 // Every timeout set since the last cleanupPopup() that has neither fired nor
 // been cleared. cleanupPopup() clears them all.
@@ -260,8 +261,10 @@ async function settle() {
 async function bootPopup(stored, options) {
     jest.resetModules();
 
-    // The three modules that reach the network. None is on the path under
+    // Three of the modules that reach the network. None is on the path under
-    // test; all would make the suite hit the internet.
+    // test; all would make the suite hit the internet. Every other request,
+    // such as the transaction screen's Blockscout lookup and the Etherscan
+    // lookup in src/shared/etherscanLabels.js, meets the fetch() stub below.
     jest.doMock("../../src/shared/prices", () => ({
         prices: {},
         refreshPrices: jest.fn(async () => {}),
@@ -334,6 +337,12 @@ async function bootPopup(stored, options) {
             windowListeners[name].push(fn);
         },
     };
+    // Every fetch() the page makes fails, as it does elsewhere in the suite,
+    // instead of reaching the internet. A new stub per boot, so its calls are
+    // that boot's requests. Put back by cleanupPopup().
+    globalThis.fetch = jest.fn(() => {
+        throw new Error("tests must not perform network requests");
+    });
     // The ten-second refresh init() starts, and a transaction wait's timers,
     // would outlive the test. So every interval is recorded rather than
     // started, clearInterval() removes it as a browser would, and tick() below
@@ -435,6 +444,7 @@ function cleanupPopup() {
     pendingTimeouts.clear();
     globalThis.setTimeout = realSetTimeout;
     globalThis.clearTimeout = realClearTimeout;
+    globalThis.fetch = realFetch;
 }
 
 module.exports = {