added quotes in unit_testing

Author: funkill

src/testing/unit_testing.md

@@ -70,8 +70,10 @@ failures:
 test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
 ```
 
-## Tests and ?
-None of the previous unit test examples had a return type. But in Rust 2018, your unit tests can return Result<()>, which lets you use `?` in them! This can make them much more concise. 
+## Tests and `?`
+None of the previous unit test examples had a return type. But in Rust 2018,
+your unit tests can return `Result<()>`, which lets you use `?` in them! This
+can make them much more concise.
 
 ```rust,editable
 fn sqrt(number: f64) -> Result<f64, String> {
@@ -95,7 +97,7 @@ mod tests {
 }
 ```
 
-See [The Edition Guide][editionguide] for more details.
+See ["The Edition Guide"][editionguide] for more details.
 
 ## Testing panics