all together, these tests can pollute each other now

src/cascadia/UnitTests_TerminalCore/ConptyRoundtripTests.cpp

@@ -3865,6 +3865,8 @@ void ConptyRoundtripTests::SimpleAltBufferTest()
     gci.LockConsole(); // Lock must be taken to manipulate alt/main buffer state.
     auto unlock = wil::scope_exit([&] { gci.UnlockConsole(); });
     sm.ProcessString(L"\x1b[?1049h");
+    // Don't leave ourselves in the alt buffer - that'll pollute other tests.
+    auto leaveAltBuffer = wil::scope_exit([&] { sm.ProcessString(L"\x1b[?1049l"); });
 
     Log::Comment(L"Painting the frame");
     VERIFY_SUCCEEDED(renderer.PaintFrame());
@@ -4024,6 +4026,8 @@ void ConptyRoundtripTests::AltBufferToAltBufferTest()
     gci.LockConsole(); // Lock must be taken to manipulate alt/main buffer state.
     auto unlock = wil::scope_exit([&] { gci.UnlockConsole(); });
     sm.ProcessString(L"\x1b[?1049h");
+    // Don't leave ourselves in the alt buffer - that'll pollute other tests.
+    auto leaveAltBuffer = wil::scope_exit([&] { sm.ProcessString(L"\x1b[?1049l"); });
 
     Log::Comment(L"Painting the frame");
     VERIFY_SUCCEEDED(renderer.PaintFrame());
@@ -4090,6 +4094,9 @@ void ConptyRoundtripTests::AltBufferResizeCrash()
 
     _checkConptyOutput = false;
 
+    // Don't leave ourselves in the alt buffer - that'll pollute other tests.
+    auto leaveAltBuffer = wil::scope_exit([&] { sm.ProcessString(L"\x1b[?1049l"); });
+
     // Note: we really don't care about the output in this test. We could, but
     // mostly we care to ensure we don't crash. If we make it through this test,
     // then it's a success.