Update some more code and text for new cargo new test content

second-edition/src/ch07-01-mod-and-the-filesystem.md

@@ -29,15 +29,16 @@ Notice that Cargo generated *src/lib.rs* instead of *src/main.rs*. Inside
 mod tests {
     #[test]
     fn it_works() {
+        assert_eq!(2 + 2, 4);
     }
 }
 ```
 
-Cargo creates an empty test to help us get our library started, rather than the
-“Hello, world!” binary that we get when we use the `--bin` option. We’ll look
-at the `#[]` and `mod tests` syntax in the “Using `super` to Access a Parent
-Module” section later in this chapter, but for now, leave this code at the
-bottom of *src/lib.rs*.
+Cargo creates an example test to help us get our library started, rather than
+the “Hello, world!” binary that we get when we use the `--bin` option. We’ll
+look at the `#[]` and `mod tests` syntax in the “Using `super` to Access a
+Parent Module” section later in this chapter, but for now, leave this code at
+the bottom of *src/lib.rs*.
 
 Because we don’t have a *src/main.rs* file, there’s nothing for Cargo to
 execute with the `cargo run` command. Therefore, we’ll use the `cargo build`

second-edition/src/ch07-03-importing-names-with-use.md

@@ -146,6 +146,7 @@ pub mod network;
 mod tests {
     #[test]
     fn it_works() {
+        assert_eq!(2 + 2, 4);
     }
 }
 ```

second-edition/src/ch11-01-writing-tests.md

@@ -120,6 +120,7 @@ Give the `it_works` function a different name, such as `exploration`, like so:
 mod tests {
     #[test]
     fn exploration() {
+        assert_eq!(2 + 2, 4);
     }
 }
 ```
@@ -148,6 +149,7 @@ like Listing 11-3:
 mod tests {
     #[test]
     fn exploration() {
+        assert_eq!(2 + 2, 4);
     }
 
     #[test]

second-edition/src/ch11-02-running-tests.md

@@ -253,7 +253,7 @@ time consuming tests with the `ignore` attribute to exclude them:
 ```rust
 #[test]
 fn it_works() {
-    assert!(true);
+    assert_eq!(2 + 2, 4);
 }
 
 #[test]