Add test for SteamWebApiInterface.

src/main/java/com/lukaspradel/steamapi/webapi/core/SteamWebApiInterface.java

@@ -30,6 +30,11 @@ private SteamWebApiInterface(String apiInterface) {
 	public static SteamWebApiInterface getInterfaceForMethod(
 			SteamWebApiInterfaceMethod interfaceMethod) {
 
+		if (interfaceMethod == null) {
+			throw new IllegalArgumentException(
+					"Unsupported Web API Interface method!");
+		}
+
 		switch (interfaceMethod) {
 
 		case GET_FRIEND_LIST:

src/test/java/com/lukaspradel/steamapi/webapi/core/SteamWebApiInterfaceTest.java

@@ -0,0 +1,60 @@
+package com.lukaspradel.steamapi.webapi.core;
+
+import static org.testng.Assert.assertEquals;
+
+import org.testng.annotations.Test;
+
+import com.lukaspradel.steamapi.BaseTest;
+
+public class SteamWebApiInterfaceTest extends BaseTest {
+
+	@Test(expectedExceptions = IllegalArgumentException.class)
+	public void testGetInterfaceMethodError() {
+
+		SteamWebApiInterface.getInterfaceForMethod(null);
+	}
+
+	@Test
+	public void testGetInterfaceMethod() {
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_FRIEND_LIST),
+				SteamWebApiInterface.I_STEAM_USER);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_GLOBAL_ACHIEVEMENT_PERCENTAGES_FOR_APP),
+				SteamWebApiInterface.I_STEAM_USER_STATS);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_NEWS_FOR_APP),
+				SteamWebApiInterface.I_STEAM_NEWS);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_OWNED_GAMES),
+				SteamWebApiInterface.I_PLAYER_SERVICE);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_PLAYER_SUMMARIES),
+				SteamWebApiInterface.I_STEAM_USER);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_RECENTLY_PLAYED_GAMES),
+				SteamWebApiInterface.I_PLAYER_SERVICE);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.GET_USER_STATS_FOR_GAME),
+				SteamWebApiInterface.I_STEAM_USER_STATS);
+
+		assertEquals(
+				SteamWebApiInterface
+						.getInterfaceForMethod(SteamWebApiInterfaceMethod.IS_PLAYING_SHARED_GAME),
+				SteamWebApiInterface.I_PLAYER_SERVICE);
+	}
+}