diff --git a/tests/test.cpp b/tests/test.cpp
index baba0f7b3e..2677c4dad6 100644
--- a/tests/test.cpp
+++ b/tests/test.cpp
@@ -109,9 +109,10 @@ static wxString FormatAssertMessage(const wxString& file,
                                     const wxString& msg)
 {
     wxString str;
-    str << "wxWidgets assert: " << cond << " failed "
-           "at " << file << ":" << line << " in " << func
-        << " with message '" << msg << "'";
+    str << wxASCII_STR("wxWidgets assert: ") << cond
+        << wxASCII_STR(" failed at ") << file << wxASCII_STR(":") << line
+        << wxASCII_STR(" in ") << func << wxASCII_STR(" with message '")
+        << msg << wxASCII_STR("'");
     return str;
 }
 
@@ -133,7 +134,7 @@ static void TestAssertHandler(const wxString& file,
     {
         // Exceptions thrown from worker threads are not caught currently and
         // so we'd just die without any useful information -- abort instead.
-        abortReason << assertMessage << "in a worker thread.";
+        abortReason << assertMessage << wxASCII_STR("in a worker thread.");
     }
 #if __cplusplus >= 201703L || wxCHECK_VISUALC_VERSION(14)
     else if ( uncaught_exceptions() )
@@ -146,12 +147,14 @@ static void TestAssertHandler(const wxString& file,
         // about why the test failed then.
         if ( s_lastAssertMessage.empty() )
         {
-            abortReason << assertMessage << "while handling an exception";
+            abortReason << assertMessage
+                        << wxASCII_STR("while handling an exception");
         }
         else // In this case the exception is due to a previous assert.
         {
-            abortReason << s_lastAssertMessage << "\n  and another "
-                        << assertMessage << " while handling it.";
+            abortReason << s_lastAssertMessage
+                        << wxASCII_STR("\n  and another ") << assertMessage
+                        << wxASCII_STR(" while handling it.");
         }
     }
     else // Can "safely" throw from here.
@@ -229,8 +232,8 @@ public:
     // show some details about the exception along the way.
     virtual bool OnExceptionInMainLoop() wxOVERRIDE
     {
-        wxFprintf(stderr, "Unhandled exception in the main loop: %s\n",
-                  Catch::translateActiveException());
+        wxFprintf(stderr, wxASCII_STR("Unhandled exception in the main loop: %s\n"),
+                  wxASCII_STR(Catch::translateActiveException().c_str()));
 
         throw;
     }
@@ -358,7 +361,7 @@ extern bool IsNetworkAvailable()
     // under Travis to avoid false positives.
     static int s_isTravis = -1;
     if ( s_isTravis == -1 )
-        s_isTravis = wxGetEnv("TRAVIS", NULL);
+        s_isTravis = wxGetEnv(wxASCII_STR("TRAVIS"), NULL);
 
     if ( s_isTravis )
         return false;
@@ -369,7 +372,7 @@ extern bool IsNetworkAvailable()
     wxSocketBase::Initialize();
 
     wxIPV4address addr;
-    if (!addr.Hostname("www.google.com") || !addr.Service("www"))
+    if (!addr.Hostname(wxASCII_STR("www.google.com")) || !addr.Service(wxASCII_STR("www")))
     {
         wxSocketBase::Shutdown();
         return false;
@@ -392,18 +395,18 @@ extern bool IsAutomaticTest()
         // Allow setting an environment variable to emulate buildslave user for
         // testing.
         wxString username;
-        if ( !wxGetEnv("WX_TEST_USER", &username) )
+        if ( !wxGetEnv(wxASCII_STR("WX_TEST_USER"), &username) )
             username = wxGetUserId();
 
         username.MakeLower();
-        s_isAutomatic = username == "buildbot" ||
-                            username.Matches("sandbox*");
+        s_isAutomatic = username == wxASCII_STR("buildbot") ||
+                            username.Matches(wxASCII_STR("sandbox*"));
 
         // Also recognize Travis and AppVeyor CI environments.
         if ( !s_isAutomatic )
         {
-            s_isAutomatic = wxGetEnv("TRAVIS", NULL) ||
-                                wxGetEnv("APPVEYOR", NULL);
+            s_isAutomatic = wxGetEnv(wxASCII_STR("TRAVIS"), NULL) ||
+                                wxGetEnv(wxASCII_STR("APPVEYOR"), NULL);
         }
     }
 
@@ -416,7 +419,7 @@ extern bool IsRunningUnderXVFB()
     if ( s_isRunningUnderXVFB == -1 )
     {
         wxString value;
-        s_isRunningUnderXVFB = wxGetEnv("wxUSE_XVFB", &value) && value == "1";
+        s_isRunningUnderXVFB = wxGetEnv(wxASCII_STR("wxUSE_XVFB"), &value) && value == wxASCII_STR("1");
     }
 
     return s_isRunningUnderXVFB == 1;
@@ -446,14 +449,14 @@ bool EnableUITests()
         // Allow explicitly configuring this via an environment variable under
         // all platforms.
         wxString enabled;
-        if ( wxGetEnv("WX_UI_TESTS", &enabled) )
+        if ( wxGetEnv(wxASCII_STR("WX_UI_TESTS"), &enabled) )
         {
-            if ( enabled == "1" )
+            if ( enabled == wxASCII_STR("1") )
                 s_enabled = 1;
-            else if ( enabled == "0" )
+            else if ( enabled == wxASCII_STR("0") )
                 s_enabled = 0;
             else
-                wxFprintf(stderr, "Unknown \"WX_UI_TESTS\" value \"%s\" ignored.\n", enabled);
+                wxFprintf(stderr, wxASCII_STR("Unknown \"WX_UI_TESTS\" value \"%s\" ignored.\n"), enabled);
         }
 
         if ( s_enabled == -1 )
@@ -616,7 +619,7 @@ int TestApp::RunTests()
     // Switch off logging to avoid interfering with the tests output unless
     // WXTRACE is set, as otherwise setting it would have no effect while
     // running the tests.
-    if ( !wxGetEnv("WXTRACE", NULL) )
+    if ( !wxGetEnv(wxASCII_STR("WXTRACE"), NULL) )
         wxLog::EnableLogging(false);
 #endif
 
diff --git a/tests/testableframe.cpp b/tests/testableframe.cpp
index 7ff54696f3..44aa2cda7c 100644
--- a/tests/testableframe.cpp
+++ b/tests/testableframe.cpp
@@ -16,7 +16,7 @@
 #include "wx/app.h"
 #include "testableframe.h"
 
-wxTestableFrame::wxTestableFrame() : wxFrame(NULL, wxID_ANY, "Test Frame")
+wxTestableFrame::wxTestableFrame() : wxFrame(NULL, wxID_ANY, wxASCII_STR("Test Frame"))
 {
     // Use fixed position to facilitate debugging.
     Move(200, 200);