Add wallet_switchEthereumChain support to snaps-jest

packages/examples/packages/ethereum-provider/snap.manifest.json

@@ -7,7 +7,7 @@
     "url": "https://github.com/MetaMask/snaps.git"
   },
   "source": {
-    "shasum": "vdxQxaJ4dDVhuIu8cvKJkKFC9YeIvaRORuCdbtX5qLM=",
+    "shasum": "u/BaDj7fzOZvB+bPRLbkBie65a5oxunLABteu1+qWns=",
     "location": {
       "npm": {
         "filePath": "dist/bundle.js",

packages/examples/packages/ethereum-provider/src/index.ts

@@ -118,7 +118,7 @@ async function personalSign(message: string, from: string) {
  * @see https://docs.metamask.io/snaps/reference/rpc-api/#wallet_invokesnap
  */
 export const onRpcRequest: OnRpcRequestHandler = async ({ request }) => {
-  const { chainId = '0x1' } = request.params as BaseParams;
+  const { chainId = '0x1' } = (request.params as BaseParams) ?? {};
   await switchChain(chainId);
 
   switch (request.method) {

packages/snaps-jest/src/internals/simulation/methods/specifications.test.ts

@@ -20,6 +20,8 @@ const MOCK_HOOKS: MiddlewareHooks = {
   createInterface: jest.fn(),
   updateInterface: jest.fn(),
   getInterfaceState: jest.fn(),
+  getIsLocked: jest.fn(),
+  resolveInterface: jest.fn(),
 };
 
 describe('resolve', () => {

packages/snaps-jest/src/internals/simulation/middleware/internal-methods/middleware.ts

@@ -4,6 +4,7 @@ import type { Json, JsonRpcParams } from '@metamask/utils';
 
 import { getAccountsHandler } from './accounts';
 import { getProviderStateHandler } from './provider-state';
+import { getSwitchEthereumChainHandler } from './switch-ethereum-chain';
 
 export type InternalMethodsMiddlewareHooks = {
   /**
@@ -19,6 +20,7 @@ const methodHandlers = {
   metamask_getProviderState: getProviderStateHandler,
   eth_requestAccounts: getAccountsHandler,
   eth_accounts: getAccountsHandler,
+  wallet_switchEthereumChain: getSwitchEthereumChainHandler,
   /* eslint-enable @typescript-eslint/naming-convention */
 };
 

packages/snaps-jest/src/internals/simulation/middleware/internal-methods/switch-ethereum-chain.test.ts

@@ -0,0 +1,28 @@
+import type { Json, PendingJsonRpcResponse } from '@metamask/utils';
+
+import { getSwitchEthereumChainHandler } from './switch-ethereum-chain';
+
+describe('getSwitchEthereumChainHandler', () => {
+  it('returns `null`', async () => {
+    const end = jest.fn();
+    const result: PendingJsonRpcResponse<Json> = {
+      jsonrpc: '2.0' as const,
+      id: 1,
+    };
+
+    await getSwitchEthereumChainHandler(
+      {
+        jsonrpc: '2.0',
+        id: 1,
+        method: 'wallet_switchEthereumChain',
+        params: [],
+      },
+      result,
+      jest.fn(),
+      end,
+    );
+
+    expect(end).toHaveBeenCalled();
+    expect(result.result).toBeNull();
+  });
+});

packages/snaps-jest/src/internals/simulation/middleware/internal-methods/switch-ethereum-chain.ts

@@ -0,0 +1,31 @@
+import type {
+  JsonRpcEngineEndCallback,
+  JsonRpcEngineNextCallback,
+} from '@metamask/json-rpc-engine';
+import type {
+  Json,
+  JsonRpcRequest,
+  PendingJsonRpcResponse,
+} from '@metamask/utils';
+
+/**
+ * A mock handler for the `wallet_switchEthereumChain` method that always
+ * returns `null`.
+ *
+ * @param _request - Incoming JSON-RPC request. This is ignored for this
+ * specific handler.
+ * @param response - The outgoing JSON-RPC response, modified to return the
+ * result.
+ * @param _next - The `json-rpc-engine` middleware next handler.
+ * @param end - The `json-rpc-engine` middleware end handler.
+ */
+export async function getSwitchEthereumChainHandler(
+  _request: JsonRpcRequest,
+  response: PendingJsonRpcResponse<Json>,
+  _next: JsonRpcEngineNextCallback,
+  end: JsonRpcEngineEndCallback,
+  // hooks: GetAccountsHandlerHooks,
+) {
+  response.result = null;
+  return end();
+}