Apply mojibake magic to test runner, too.

core/testing/runner.odin

@@ -267,6 +267,10 @@ runner :: proc(internal_tests: []Internal_Test) -> bool {
 		}
 	}
 
+	when ODIN_OS == .Windows {
+		set_utf8_codepage()
+		defer restore_old_codepage()
+	}
 
 	// `-vet` needs parameters to be shadowed by themselves first as an
 	// explicit declaration, to allow the next line to work.

core/testing/terminal_window.odin

@@ -0,0 +1,16 @@
+#+private
+#+build windows
+package testing
+
+import win32 "core:sys/windows"
+
+old_console_codepage: win32.CODEPAGE
+
+set_utf8_codepage :: proc() {
+	old_console_codepage = win32.GetConsoleOutputCP()
+	win32.SetConsoleOutputCP(win32.CODEPAGE(65001))
+}
+
+restore_old_codepage :: proc() {
+	win32.SetConsoleOutputCP(old_console_codepage)
+}