diff --git a/src/file_handler.cpp b/src/file_handler.cpp
index d0783431808..1c7f98e9b3b 100644
--- a/src/file_handler.cpp
+++ b/src/file_handler.cpp
@@ -31,16 +31,7 @@ namespace file_handler {
     }
 
     std::ifstream in(path);
-
-    std::string input;
-    std::string base64_cert;
-
-    while (!in.eof()) {
-      std::getline(in, input);
-      base64_cert += input + '\n';
-    }
-
-    return base64_cert;
+    return std::string { (std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>() };
   }
 
   /**
diff --git a/tests/unit/test_file_handler.cpp b/tests/unit/test_file_handler.cpp
index 9167b53de77..b77ba6188cc 100644
--- a/tests/unit/test_file_handler.cpp
+++ b/tests/unit/test_file_handler.cpp
@@ -6,14 +6,54 @@
 
 #include <tests/conftest.cpp>
 
-TEST(FileHandlerTests, WriteFileTest) {
-  EXPECT_EQ(file_handler::write_file("write_file_test.txt", "test"), 0);
+class FileHandlerTests: public virtual BaseTest, public ::testing::WithParamInterface<std::tuple<int, std::string>> {
+protected:
+  void
+  SetUp() override {
+    BaseTest::SetUp();
+  }
+
+  void
+  TearDown() override {
+    BaseTest::TearDown();
+  }
+};
+INSTANTIATE_TEST_SUITE_P(
+  TestFiles,
+  FileHandlerTests,
+  ::testing::Values(
+    std::make_tuple(0, ""),  // empty file
+    std::make_tuple(1, "a"),  // single character
+    std::make_tuple(2, "Mr. Blue Sky - Electric Light Orchestra"),  // single line
+    std::make_tuple(3, R"(
+Morning! Today's forecast calls for blue skies
+The sun is shining in the sky
+There ain't a cloud in sight
+It's stopped raining
+Everybody's in the play
+And don't you know, it's a beautiful new day
+Hey, hey, hey!
+Running down the avenue
+See how the sun shines brightly in the city
+All the streets where once was pity
+Mr. Blue Sky is living here today!
+Hey, hey, hey!
+    )")  // multi-line
+    ));
+
+TEST_P(FileHandlerTests, WriteFileTest) {
+  auto [fileNum, content] = GetParam();
+  std::string fileName = "write_file_test_" + std::to_string(fileNum) + ".txt";
+  EXPECT_EQ(file_handler::write_file(fileName.c_str(), content), 0);
 }
 
-TEST(FileHandlerTests, ReadFileTest) {
-  // read file from WriteFileTest
-  EXPECT_EQ(file_handler::read_file("write_file_test.txt"), "test\n");  // sunshine adds a newline
+TEST_P(FileHandlerTests, ReadFileTest) {
+  auto [fileNum, content] = GetParam();
+  std::string fileName = "write_file_test_" + std::to_string(fileNum) + ".txt";
+  EXPECT_EQ(file_handler::read_file(fileName.c_str()), content);
+}
 
+TEST(FileHandlerTests, ReadMissingFileTest) {
   // read missing file
   EXPECT_EQ(file_handler::read_file("non-existing-file.txt"), "");
 }