The \mintinline{rust}|Result<T, E>| type has many helper methods defined on it to do various, more specific tasks. If the Result value is the Ok variant, unwrap will return the value inside the Ok. If the Result is the Err variant, unwrap will call the panic! macro for us.

\begin{itemize}

\item The \mintinline{rust}|?| operator can only be used in functions whose return type is compatible with the value the \mintinline{rust}|?| is used on.

\item we’re only allowed to use the ? operator in a function that returns \mintinline{rust}|Result|, \mintinline{rust}|Option|, or another type that implements \mintinline{rust}|FromResidual|.

\end{itemize}

\inputminted{rust}{./code/generic1.rs}

\inputminted{rust}{./code/generic2.rs}

\inputminted[fontsize=\scriptsize]{rust}{./code/generic3.rs}

Monomorphization is the process of turning generic code into specific code by filling in the concrete types that are used when \textbf{compiled}. In this process, the compiler does the opposite of the steps we used to create the generic function: the compiler looks at all the places where generic code is called and generates code for the concrete types the generic code is called with.

\inputminted[fontsize=\scriptsize]{rust}{./code/Trait1.rs}

\begin{itemize}

\item Lifetime annotations \textbf{don’t change how long any of the references live}. Rather, they \textbf{describe the relationships of the lifetimes of multiple references to each other }without affecting the lifetimes.

\item Lifetime annotations have a slightly \textbf{unusual syntax}: the names of lifetime parameters must start with an apostrophe (') and are usually all lowercase and very short, like generic types. Most people use the name \mintinline{rust}|'a| for the first lifetime annotation. We place lifetime parameter annotations after the \mintinline{rust}|&| of a reference, using a space to separate the annotation from the reference’s type.

\inputminted{rust}{./code/lifetime3.rs}

\end{itemize}

The generic lifetime \mintinline{rust}|'a| will get the concrete \textbf{lifetime that is equal to the smaller of the lifetimes }of x and y. In practice, it means that the lifetime of the reference returned by the longest function is the same as the smaller of the lifetimes of the values referred to by the function arguments. These relationships are what we want Rust to use when analyzing this code.

\begin{frame}[fragile]

\frametitle{Lifetime Annotations in Function Signatures (3)}

\inputminted{shell}{./code/lifetime5.shell}

\end{frame}

\item Sometimes a few specific tests can be very time-consuming to execute, so you might want to exclude them during most runs of \mintinline{shell}|cargo test|. After \mintinline{shell}|#[test]| we add the \mintinline{shell}|#[ignore]| line to the test we want to exclude. If we want to run only the ignored tests, we can use \mintinline{shell}|cargo test -- --ignored|.

\inputminted[fontsize=\scriptsize]{rust}{./code/test8.rs}

\begin{itemize}

\item Unit tests are small and more focused, \textbf{testing one module in isolation at a time}, and \textbf{can test private interfaces}. You’ll put unit tests in the \mintinline{shell}|src| directory in each file with the code that they’re testing. The convention is to create a module named tests in each file to contain the test functions and to annotate the module with \mintinline{rust}|#[cfg(test)]|.

\item Integration tests are entirely external to your library and use your code in the same way any other external code would,\textbf{ using only the public interface and potentially exercising multiple modules per test}. Their purpose is to test \textbf{whether many parts of your library work together correctly}.

\end{itemize}

\begin{columns}

\column{0.4\textwidth}

\begin{figure}

\centering

\includegraphics[width=0.8\linewidth]{img/test.png}

\end{figure}

\column{0.6\textwidth}

\scriptsize

Filename: \mintinline{shell}|tests/integration_test.rs|

\inputminted[fontsize=\scriptsize]{rust}{./code/test9.rs}

\mintinline{shell}|$ cargo test|

\mintinline{shell}|$ cargo test --test integration_test|

\end{columns}

Filename: \mintinline{shell}|tests/common.rs|

Filename: \mintinline{shell}|tests/integration_test.rs|

\inputminted[fontsize=\scriptsize]{rust}{./code/test11.rs}

\section{An I/O Project: Building a Command Line Program}