diff --git a/packages/babel-helper-transform-fixture-test-runner/src/index.ts b/packages/babel-helper-transform-fixture-test-runner/src/index.ts
index 459388d7e8..ca938f2497 100644
--- a/packages/babel-helper-transform-fixture-test-runner/src/index.ts
+++ b/packages/babel-helper-transform-fixture-test-runner/src/index.ts
@@ -196,6 +196,26 @@ export function runCodeInTestContext(
   }
 }
 
+function maybeMockConsole(validateLogs, run) {
+  const actualLogs = { stdout: "", stderr: "" };
+
+  if (!validateLogs) return { result: run(), actualLogs };
+
+  const spy1 = jest.spyOn(console, "log").mockImplementation(msg => {
+    actualLogs.stdout += `${msg}\n`;
+  });
+  const spy2 = jest.spyOn(console, "warn").mockImplementation(msg => {
+    actualLogs.stderr += `${msg}\n`;
+  });
+
+  try {
+    return { result: run(), actualLogs };
+  } finally {
+    spy1.mockRestore();
+    spy2.mockRestore();
+  }
+}
+
 function run(task) {
   const {
     actual,
@@ -234,7 +254,13 @@ function run(task) {
   if (execCode) {
     const context = createContext();
     const execOpts = getOpts(exec);
-    result = babel.transform(execCode, execOpts);
+
+    // Ignore Babel logs of exec.js files.
+    // They will be validated in input/output files.
+    ({ result } = maybeMockConsole(validateLogs, () =>
+      babel.transform(execCode, execOpts),
+    ));
+
     checkDuplicatedNodes(babel, result.ast);
     execCode = result.code;
 
@@ -251,24 +277,11 @@ function run(task) {
   const inputCode = actual.code;
   const expectedCode = expected.code;
   if (!execCode || inputCode) {
-    const actualLogs = { stdout: "", stderr: "" };
-    let restoreSpies = null;
-    if (validateLogs) {
-      const spy1 = jest.spyOn(console, "log").mockImplementation(msg => {
-        actualLogs.stdout += `${msg}\n`;
-      });
-      const spy2 = jest.spyOn(console, "warn").mockImplementation(msg => {
-        actualLogs.stderr += `${msg}\n`;
-      });
-      restoreSpies = () => {
-        spy1.mockRestore();
-        spy2.mockRestore();
-      };
-    }
+    let actualLogs;
 
-    result = babel.transform(inputCode, getOpts(actual));
-
-    if (restoreSpies) restoreSpies();
+    ({ result, actualLogs } = maybeMockConsole(validateLogs, () =>
+      babel.transform(inputCode, getOpts(actual)),
+    ));
 
     const outputCode = normalizeOutput(result.code);
 
diff --git a/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/generator-yield/stderr.txt b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/generator-yield/stderr.txt
new file mode 100644
index 0000000000..57a1da31d1
--- /dev/null
+++ b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/generator-yield/stderr.txt
@@ -0,0 +1 @@
+The smart-mix pipe operator is deprecated. Use "proposal": "hack" instead.
diff --git a/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/hash-tuple/stderr.txt b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/hash-tuple/stderr.txt
new file mode 100644
index 0000000000..57a1da31d1
--- /dev/null
+++ b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/hash-tuple/stderr.txt
@@ -0,0 +1 @@
+The smart-mix pipe operator is deprecated. Use "proposal": "hack" instead.
diff --git a/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/if-else-block/stderr.txt b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/if-else-block/stderr.txt
new file mode 100644
index 0000000000..57a1da31d1
--- /dev/null
+++ b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/if-else-block/stderr.txt
@@ -0,0 +1 @@
+The smart-mix pipe operator is deprecated. Use "proposal": "hack" instead.
diff --git a/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/options.json b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/options.json
index ffe4feed49..475ac06423 100644
--- a/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/options.json
+++ b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/options.json
@@ -1,3 +1,4 @@
 {
+  "validateLogs": true,
   "plugins": [["proposal-pipeline-operator", { "proposal": "smart" }]]
 }
diff --git a/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/pipe-body-with-topic-method-call/stderr.txt b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/pipe-body-with-topic-method-call/stderr.txt
new file mode 100644
index 0000000000..57a1da31d1
--- /dev/null
+++ b/packages/babel-plugin-proposal-pipeline-operator/test/fixtures/smart/pipe-body-with-topic-method-call/stderr.txt
@@ -0,0 +1 @@
+The smart-mix pipe operator is deprecated. Use "proposal": "hack" instead.
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/input.ts b/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/input.ts
index a5ff19e60d..16fbbe08a3 100644
--- a/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/input.ts
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/input.ts
@@ -1,3 +1 @@
 export declare enum A {}
-
-;
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/output.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/output.mjs
index 092bc2b041..cb0ff5c3b5 100644
--- a/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/output.mjs
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/declarations/export-declare-enum/output.mjs
@@ -1 +1 @@
-;
+export {};