Merge pull request #3497 from regexident/swap-assert-eq-arg-order

Swap inconsistent `assert_eq!` argument order in testing chapter

listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/output.txt

@@ -9,10 +9,9 @@ test tests::it_adds_two ... FAILED
 failures:
 
 ---- tests::it_adds_two stdout ----
-thread 'tests::it_adds_two' panicked at src/lib.rs:11:9:
 assertion `left == right` failed
-  left: 4
- right: 5
+  left: 5
+ right: 4
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 
 

listings/ch11-writing-automated-tests/no-listing-04-bug-in-add-two/src/lib.rs

@@ -10,6 +10,6 @@ mod tests {
 
     #[test]
     fn it_adds_two() {
-        assert_eq!(4, add_two(2));
+        assert_eq!(add_two(2), 4);
     }
 }

src/ch11-01-writing-tests.md

@@ -317,7 +317,7 @@ assertion functions are called `expected` and `actual`, and the order in which
 we specify the arguments matters. However, in Rust, they’re called `left` and
 `right`, and the order in which we specify the value we expect and the value
 the code produces doesn’t matter. We could write the assertion in this test as
-`assert_eq!(add_two(2), 4)`, which would result in the same failure message
+`assert_eq!(4, add_two(2))`, which would result in the same failure message
 that displays `` assertion failed: `(left == right)` ``.
 
 The `assert_ne!` macro will pass if the two values we give it are not equal and