Make null checks more descriptive (#1688)

wpilibj/src/test/java/edu/wpi/first/wpilibj/util/ErrorMessagesTest.java

@@ -0,0 +1,33 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018-2019 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj.util;
+
+import org.junit.jupiter.api.Test;
+
+import edu.wpi.first.wpilibj.UtilityClassTest;
+
+import static edu.wpi.first.wpilibj.util.ErrorMessages.requireNonNullParam;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class ErrorMessagesTest extends UtilityClassTest {
+  ErrorMessagesTest() {
+    super(ErrorMessages.class);
+  }
+
+  @Test
+  void requireNonNullParamNullTest() {
+    assertThrows(NullPointerException.class, () -> requireNonNullParam(null, "testParam",
+        "testMethod"));
+  }
+
+  @Test
+  void requireNonNullParamNotNullTest() {
+    assertDoesNotThrow(() -> requireNonNullParam("null", "testParam", "testMethod"));
+  }
+}