Fix unexpected GitHub Actions failures (#7980)

tests_integration/__tests__/check.js

@@ -27,10 +27,8 @@ describe("--checks works in CI just as in a non-TTY mode", () => {
     "cli/write",
     ["--check", "formatted.js", "unformatted.js"],
     {
-      env: {
-        CI: "true",
-      },
       stdoutIsTTY: true,
+      ci: true,
     }
   ).test({
     status: 1,

tests_integration/__tests__/list-different.js

@@ -27,10 +27,8 @@ describe("--list-different works in CI just as in a non-TTY mode", () => {
     "cli/write",
     ["--list-different", "formatted.js", "unformatted.js"],
     {
-      env: {
-        CI: "true",
-      },
       stdoutIsTTY: true,
+      ci: true,
     }
   ).test({
     status: 1,

tests_integration/runPrettier.js

@@ -62,13 +62,11 @@ function runPrettier(dir, args, options) {
   const originalExitCode = process.exitCode;
   const originalStdinIsTTY = process.stdin.isTTY;
   const originalStdoutIsTTY = process.stdout.isTTY;
-  const originalEnv = process.env;
 
   process.chdir(normalizeDir(dir));
   process.stdin.isTTY = !!options.isTTY;
   process.stdout.isTTY = !!options.stdoutIsTTY;
   process.argv = ["path/to/node", "path/to/prettier/bin"].concat(args);
-  process.env = { ...process.env, ...options.env };
 
   jest.resetModules();
 
@@ -80,7 +78,7 @@ function runPrettier(dir, args, options) {
     .mockImplementation(() => SynchronousPromise.resolve(options.input || ""));
   jest
     .spyOn(require(thirdParty), "isCI")
-    .mockImplementation(() => process.env.CI);
+    .mockImplementation(() => !!options.ci);
   jest
     .spyOn(require(thirdParty), "cosmiconfig")
     .mockImplementation((moduleName, options) =>
@@ -113,7 +111,6 @@ function runPrettier(dir, args, options) {
     process.exitCode = originalExitCode;
     process.stdin.isTTY = originalStdinIsTTY;
     process.stdout.isTTY = originalStdoutIsTTY;
-    process.env = originalEnv;
     jest.restoreAllMocks();
   }