feat test: array converter for parametrized tests

assignment/src/test/java/appointmentplanner/StringArrayConverter.java

@@ -0,0 +1,18 @@
+package appointmentplanner;
+
+import org.junit.jupiter.params.converter.ArgumentConversionException;
+import org.junit.jupiter.params.converter.SimpleArgumentConverter;
+
+public class StringArrayConverter extends SimpleArgumentConverter {
+
+  @Override
+  protected Object convert(Object source, Class<?> targetType) throws ArgumentConversionException {
+    if (source instanceof String && String[].class.isAssignableFrom(targetType)) {
+      return ((String) source).split("\\s*,\\s*");
+    } else {
+      throw new IllegalArgumentException("Conversion from " + source.getClass() + " to "
+          + targetType + " not supported.");
+    }
+  }
+
+}