fix tests

src/App.js

@@ -43,7 +43,7 @@ const i18nProvider = polyglotI18nProvider(
   resolveBrowserLocale()
 );
 
-const defaultTheme = createTheme();
+const theme = createTheme();
 const generateClassName = createGenerateClassName({
   disableGlobal: true,
   seed: "mui-jss",
@@ -51,7 +51,7 @@ const generateClassName = createGenerateClassName({
 
 const App = () => (
   <StylesProvider generateClassName={generateClassName}>
-    <ThemeProvider theme={defaultTheme}>
+    <ThemeProvider theme={theme}>
       <Admin
         disableTelemetry
         loginPage={LoginPage}

src/components/LoginPage.test.js

@@ -1,14 +1,19 @@
 import React from "react";
 import { render } from "@testing-library/react";
 import { TestContext } from "ra-test";
+import { createTheme, ThemeProvider } from "@mui/material/styles";
 import LoginPage from "./LoginPage";
 
+const theme = createTheme();
+
 describe("LoginForm", () => {
   it("renders", () => {
     render(
-      <TestContext>
+      <ThemeProvider theme={theme}>
-        <LoginPage />
+        <TestContext>
-      </TestContext>
+          <LoginPage />
+        </TestContext>
+      </ThemeProvider>
     );
   });
 });