Add some exercises about tests!

tests/tests2.rs

@@ -0,0 +1,43 @@
+// This test has a problem with it -- make the test compile! Make the test
+// pass! Make the test fail! Scroll down for hints :)
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn you_can_assert_eq() {
+        assert_eq!();
+    }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+// Like the previous exercise, you don't need to write any code to get this test to compile and
+// run. `assert_eq!` is a macro that takes two arguments and compares them. Try giving it two
+// values that are equal! Try giving it two arguments that are different! Try giving it two values
+// that are of different types! Try switching which argument comes first and which comes second!