add test for uploading a file

src/test/java/org/selenide/lt/FileUploadTest.java

@@ -0,0 +1,32 @@
+package org.selenide.lt;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.Writer;
+
+import static com.codeborne.selenide.Condition.text;
+import static com.codeborne.selenide.Selenide.$;
+import static com.codeborne.selenide.Selenide.open;
+
+class FileUploadTest {
+  @Test
+  void canUploadFile() throws IOException {
+    File file = createTemporaryFile();
+
+    open("https://the-internet.herokuapp.com/upload");
+    $("#file-upload").uploadFile(file);
+    $("#file-submit").click();
+    $("#uploaded-files").shouldHave(text(file.getName()));
+  }
+
+  private File createTemporaryFile() throws IOException {
+    File tempFile = File.createTempFile("selenide-lambdatest.", ".temp.txt");
+    try (Writer w = new FileWriter(tempFile)) {
+      w.write("Hello, world!");
+    }
+    return tempFile;
+  }
+}