add TestIO

src/test/scala/testIO.scala

@@ -0,0 +1,25 @@
+package introprog
+
+val tmpDir = "target/tmp"
+
+class TestIO extends munit.FunSuite {
+  test("TestIO: createDirIfNotExist, saveString, appendString, loadLines, appendLines") {
+    val existed = IO.createDirIfNotExist(tmpDir)
+    assert(IO.isExisting(tmpDir), s"dir should exists: $tmpDir")
+    val s1 = "hello"
+    val fn = s"$tmpDir/hello.txt"
+    IO.saveString(s1, fileName = fn)
+    val s2 = IO.loadString(fileName = fn)
+    assertEquals(s1, s2, "saved string different from loaded")
+    IO.appendString("!\n", fileName = fn )
+    val s3 = IO.loadString(fileName = fn)
+    assertEquals(s3, s2 + "!\n", "saved string is missing appended '!+newline'")
+    IO.appendLines(Seq("line2"),fileName = fn)
+    val s4 = IO.loadLines(fileName = fn)
+    assertEquals(s4, Vector("hello!", "line2"), s"loadLines not as expected: $s4")
+    val s5 = IO.loadString(fileName = fn)
+    assertEquals(s5, "hello!\nline2\n", s"loadLines not as expected: $s5")
+    IO.appendLines(Seq(),fileName = fn) // nothing should be added, not even newline
+    assertEquals(s5, IO.loadString(fileName = fn), s"loadLines not as expected: $s5")
+  }
+}