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//! A collection of useful assertions and other utilities for writing //! tests in Rust. use std::any::Any; use std::ops::Deref; /// Get the panic message as a `&str`, if available /// /// While a panic value can be any type, *usually* it is either a `String` /// or a `str`, hidden inside a `Box<dyn Any + Send + Sync>` (see /// [`std::thread::Result`] for more info). This function gets the panic /// message as an &str (if available) from a panic value. /// /// ``` /// use std::panic::catch_unwind; /// use cool_asserts::get_panic_message; /// /// let result = catch_unwind(|| panic!("{}, {}!", "Hello", "World")); /// let panic = result.unwrap_err(); /// let message = get_panic_message(&panic).unwrap(); /// /// assert_eq!(message, "Hello, World!"); #[inline] pub fn get_panic_message(panic: &Box<dyn Any + Send>) -> Option<&str> { panic.downcast_ref::<String>() .map(String::as_str) .or_else(|| panic.downcast_ref::<&'static str>().map(Deref::deref)) } #[cfg(test)] mod test_get_panic_message { use std::panic::catch_unwind; use super::get_panic_message; #[test] fn str_message() { let result = catch_unwind(|| panic!("Hello, World!")) .expect_err("Function didn't panic????"); assert_eq!(get_panic_message(&result), Some("Hello, World!")); } #[test] fn string_message() { let result = catch_unwind(|| panic!("Hello, World!".to_string())) .expect_err("Function didn't panic????"); assert_eq!(get_panic_message(&result), Some("Hello, World!")); } #[test] fn formatted_message() { let result = catch_unwind(|| panic!("{}, {}!", "Hello", "World")) .expect_err("Function didn't panic????"); assert_eq!(get_panic_message(&result), Some("Hello, World!")); } #[test] fn other_message() { let result = catch_unwind(|| panic!(25)) .expect_err("Function didn't panic????"); assert_eq!(get_panic_message(&result), None); } } /// Compute the max of list of expressions. /// /// This is given as a macro so that it can be fully evaluated at compile /// time. /// /// It guarantees that: /// /// - All the expressions are evaluated in order, if relevant /// - Each expression is only evaluated once. #[macro_export] #[doc(hidden)] macro_rules! max { ($value:expr $(,)?) => ($value); ($lhs:expr $(, $tail:expr)+ $(,)?) => {{ let lhs = $lhs; let tail = $crate::max!($($tail),+); if lhs < tail { tail } else { lhs } }} } /// Get a partial format string for assertion_failure given the spec #[macro_export] #[doc(hidden)] macro_rules! make_assertion_failure_fmt { () => {"\n {:>padding$}: {}"}; (debug) => {"\n {:>padding$}: {:?}"}; } #[macro_export] #[doc(hidden)] macro_rules! make_assertion_failure_tail { () => {}; ($($_arg:tt)+) => { "\n {}" }; } /// Panic with an assertion failure message /// /// This macro is used in failing assertions to issue a panic with a message /// in a standardized format, which includes: /// /// - A static description of what went wrong. /// - The file and line number of the error. /// - Optionally, key-value components of the failed assertion (for example, /// the `lhs` and `rhs` of a failed `assert_eq!`). These components are /// visually aligned for an easier debugging experience. /// - Optionally, a trailing formatted message. /// /// The format of this macro is designed to be similar to the message printed /// by [`assert_eq!`] or [`assert_ne!`]. The exact output is not currently /// guaranteed to be identical with matching semver versions, though this may /// change in the future. /// /// # Example: /// /// ``` /// use std::panic::catch_unwind; /// use cool_asserts::{assertion_failure, get_panic_message}; /// /// let result = catch_unwind(|| assertion_failure!( /// "Assertion Message", /// // Add key-value data to the debug message /// key: 10, /// /// // Use the "debug" keyword to debug-print something. /// // Additionally, notice in the output that the key and long-key /// // are visually aligned. /// long_key debug: "Hello\tWorld!"; /// /// // After a semicolon, add a trailing format message /// "Trailing message: {}, {}!", "Hello", "World" /// )); /// let panic = result.unwrap_err(); /// let message = get_panic_message(&panic).unwrap(); /// assert_eq!( /// message, /// r#"assertion failed at src/lib.rs:7: `(Assertion Message)` /// key: 10 /// long_key: "Hello\tWorld!" /// Trailing message: Hello, World!"# /// ); /// ``` #[macro_export] macro_rules! assertion_failure { ($message:literal $($(, $key:ident $($spec:ident)?: $value:expr)+)? $(; $($fmt:tt)+)? ) => { panic!( concat!( "assertion failed at {file}:{line}: `(", $message, ")`", $($($crate::make_assertion_failure_fmt!($($spec)?),)+)? $($crate::make_assertion_failure_tail!($($fmt)+),)? ), $($(stringify!($key), $value,)+)? $(format_args!($($fmt)+),)? $(padding = $crate::max!($(stringify!($key).len(),)+),)? file=file!(), line=line!(), ) }; ($message:literal $($(, $key:ident $($spec:ident)?: $value:expr)+)? ,) => { $crate::assertion_failure!($message $($(, $key $($spec)?: $value)+)?) }; ($message:literal $($(, $key:ident $($spec:ident)?: $value:expr)+)? ;) => { $crate::assertion_failure!($message $($(, $key $($spec)?: $value)+)?) }; } #[cfg(test)] mod assertion_failure_tests { use super::{assertion_failure, assert_panics}; #[test] fn just_message() { assert_panics!( assertion_failure!("Failure Message"), includes("assertion failed at"), includes("Failure Message"), excludes("\n"), ) } #[test] fn keys_aligned() { assert_panics!( assertion_failure!( "Failure Message", key: 10, long_key: 20, ), includes("assertion failed at"), includes("Failure Message"), includes(" key: 10\n"), includes("long_key: 20"), ); } #[test] fn keys_trailing_fmt() { assert_panics!( assertion_failure!( "Failure Message", key: 10, long_key: 20; "{}, {}!", "Hello", "World" ), includes("assertion failed at"), includes("Failure Message"), includes(" key: 10\n"), includes("long_key: 20\n"), includes("\n Hello, World!") ); } } /// Assert that the value of an expression matches a given pattern. /// /// This assertion checks that the value of an expression matches a pattern. /// It panics if the expression does not match. /// /// Optionally, provide a block with `=> { <block> }`; the block will be run /// with the matched pattern if the match was successful. This allows running /// additional assertions on the matched pattern. /// /// You can also add a trailing format message that will be included with /// the panic in the event of an assertion failure, just like with /// [`assert_eq!`]. /// /// # Example /// /// ``` /// use cool_asserts::{assert_matches, assert_panics}; /// /// assert_panics!{ /// assert_matches!(Some(10), None), /// includes("value does not match pattern"), /// } /// /// assert_matches!(Some(10), Some(x) => { /// assert_eq!(x, 10); /// }) /// ``` #[macro_export] macro_rules! assert_matches { ($expression:expr, $pattern:pat $(if $guard:expr)? $(=> $block:expr)?, ) => { $crate::assert_matches!($expression, $pattern $(if $guard)? $(=> $block)?) }; ($expression:expr, $pattern:pat $(if $guard:expr)? $(=> $block:expr)? $(, $($fmt_arg:tt)+)?) => ({ match $expression { $pattern $(if $guard)? => { $($block)? }, v => $crate::assertion_failure!( "value does not match pattern", value debug: v, pattern: stringify!($pattern $(if $guard)?) $(; $($fmt_arg)+)? ) } }); } #[cfg(test)] mod test_assert_matches { use super::{assert_matches, assert_panics}; #[derive(Debug)] struct TestStruct { x: isize, y: isize, } const TEST_VALUE: Option<TestStruct> = Some(TestStruct { x: 10, y: 20 }); #[test] fn basic_case() { assert_matches!(TEST_VALUE, Some(_)); } #[test] fn trailing_comma() { assert_matches!(TEST_VALUE, Some(_),); } #[test] fn basic_guard() { assert_matches!(TEST_VALUE, Some(v) if v.y == 20); } #[test] fn basic_block() { assert_matches!(TEST_VALUE, Some(v) => { assert_eq!(v.x, 10); }) } #[test] fn basic_guard_block() { assert_matches!(TEST_VALUE, Some(v) if v.y == 20 => { assert_eq!(v.x, 10); }) } #[test] fn basic_failure() { assert_panics!( assert_matches!(TEST_VALUE, None), includes("assertion failed"), includes("value does not match pattern"), includes("pattern: None"), includes(&format!("value: {:?}", TEST_VALUE)) ); } #[test] fn basic_guard_failure() { assert_panics!( assert_matches!(TEST_VALUE, Some(v) if v.y == 0), includes("assertion failed"), includes("value does not match pattern"), includes("pattern: Some(v) if v.y == 0"), includes(&format!("value: {:?}", TEST_VALUE)) ); } #[test] fn basic_block_failure() { assert_panics!( assert_matches!(TEST_VALUE, None => {panic!("Custom Panic")}), includes("assertion failed"), includes("value does not match pattern"), includes("pattern: None"), includes(&format!("value: {:?}", TEST_VALUE)), excludes("Custom Panic"), ); } #[test] fn failure_in_block() { assert_panics!( assert_matches!(TEST_VALUE, Some(TestStruct{..}) => {panic!("Custom Panic")}), includes("Custom Panic"), excludes("assertion failed"), excludes("value does not match pattern"), ) } } /// Assert that an expression panics. /// /// This macro asserts that a given expression panics. If the expression /// doesn't panic, this macro will panic, with a description including the /// expression itself, as well as the return value of the expression. /// /// This macro is intended to replace `#[should_panic]` in rust tests: /// /// - It allows for checking that a particular expression or statement panics, /// rather than an entire test function. /// - It allows checking for the presence or absence of multiple substrings. /// `should_panic` can only test for a single substring (with `expected`), /// and can't test for absence at all. /// /// ## Examples /// /// ``` /// use cool_asserts::assert_panics; /// /// assert_panics!({ /// let _x = 1 + 2; /// panic!("Panic Message"); /// }); /// ``` /// ```should_panic /// use cool_asserts::assert_panics; /// /// assert_panics!(1 + 2); /// ``` /// /// # Substring checking /// /// Optionally, provide a list of conditions of the form `includes(pattern)` /// or `excludes(pattern)`. If given, the assertion will check that the /// panic message contains or does not contain each of the given patterns. /// It uses [`str::contains`], which means that anything /// implementing [`Pattern`][::std::str::Pattern] can be used as a matcher. /// /// ## Examples /// /// ``` /// use cool_asserts::assert_panics; /// /// assert_panics!( /// panic!("Custom message: {}", "message"), /// includes("message: message"), /// includes("Custom"), /// excludes("Foo"), /// ); /// ``` /// /// ```should_panic /// // THIS EXAMPLE PANICS /// /// use cool_asserts::assert_panics; /// /// // The expression panics, which passes the assertion, but it fails /// // the message test, which means the overall assertion fails. /// assert_panics!( /// panic!("Message"), /// excludes("Message") /// ); /// ``` /// /// # Generic message testing /// /// If the `includes(..)` and `excludes(..)` are not powerful enough, /// `assert_panics` can also accept a closure as an argument. If the expression /// panics, the closure is called with the panic message as an `&str`. This /// closure can contain any additional assertions you wish to perform on the /// panic message. /// /// ## Examples /// /// ``` /// use cool_asserts::assert_panics; /// /// assert_panics!(panic!("{}, {}!", "Hello", "World"), |msg| { /// assert_eq!(msg, "Hello, World!") /// }); /// ``` /// ``` /// use cool_asserts::assert_panics; /// /// assert_panics!( /// assert_panics!( /// panic!("Message"), /// |msg| panic!("Custom Message") /// ), /// includes("Custom Message"), /// excludes("assertion failed") /// ) /// ``` /// /// # Generic panic values /// /// If you need to test panics that aren't event messages– that is, that aren't /// [`String`] or `&str` values provided by most panics (including most /// assertions)– you can provide a reference type in the closure. The macro /// will attermpt to cast the panic value to that type. It will fail the /// assertion if the type doesn't match; otherwise the closure will be called. /// /// ``` /// use cool_asserts::assert_panics; /// /// assert_panics!(panic!(10i64), |value: &i64| { /// assert_eq!(value, &10); /// }) /// ``` /// /// ``` /// use cool_asserts::assert_panics; /// /// assert_panics!( /// assert_panics!( /// panic!(10i64), /// |value: &i32| { /// panic!("CUSTOM PANIC"); /// } /// ), /// includes("expression panic type mismatch"), /// includes("i32"), /// // Currently, type_name of Any returns &dyn Any, rather than the actual type /// // includes("i64"), /// excludes("expression didn't panic"), /// excludes("CUSTOM PANIC") /// ); /// ``` #[macro_export] macro_rules! assert_panics { ($expression:expr, |$panic:ident: Box<$(dyn)? Any $(+ Send)? $(+ 'static)?>| $body:expr) => ( match ::std::panic::catch_unwind(|| {$expression}) { Ok(result) => $crate::assertion_failure!( "expression didn't panic", expression: stringify!($expression), returned debug: result ), Err($panic) => { $body } } ); ($expression:expr, |$msg:ident $(: &str)?| $body:expr) => ( $crate::assert_panics!($expression, |panic: Box<dyn Any>| { let $msg: &str = $crate::get_panic_message(&panic) .unwrap_or_else(|| $crate::assertion_failure!( "expression panic type wasn't String or &str", expression: stringify!($expression), )); { $body } }) ); ($expression:expr, |$value:ident: &$type:ty| $body:expr) => ( $crate::assert_panics!($expression, |panic: Box<dyn Any>| { fn ref_type_name<T: ?Sized>(_value: &T) -> &'static str { ::core::any::type_name::<T>() } let $value: &$type = panic.downcast_ref() .unwrap_or_else(|| $crate::assertion_failure!( "expression panic type mismatch", expression: stringify!($expression), expected: stringify!($type), actual: ref_type_name(&panic), ) ); { $body } }) ); ($expression:expr $(,)?) => ( $crate::assert_panics!($expression, |_panic: Box<dyn Any>| {}) ); ($expression:expr $(, $rule:ident($arg:expr))+ $(,)?) => { $crate::assert_panics!($expression, |msg| { $($crate::check_rule!($expression, msg, $rule($arg));)+ }) } } #[macro_export] #[doc(hidden)] macro_rules! check_rule { ($expression:expr, $msg:ident, includes($incl:expr)) => ( if !$msg.contains($incl) { $crate::assertion_failure!( "panic message didn't include expected string", expression: stringify!($expression), message debug: $msg, expected debug: $incl, ); } ); ($expression:expr, $msg:ident, excludes($excl:expr)) => ( if $msg.contains($excl) { $crate::assertion_failure!( "panic message included disallowed string", expression: stringify!($expression), message debug: $msg, disallowed debug: $excl, ); } ); } #[cfg(test)] mod test_assert_panics { use super::assert_panics; mod bootstrap_tests { use super::assert_panics; // We use a few should_panic tests to bootstrap– ensure that assert_panics // basically works– then we do the more complex testing with itself. // If all these tests pass, assert_panics has at least enough working // that it can test itself more thoroughly. #[test] fn passes_with_panic() { assert_panics!(panic!()); } #[test] #[should_panic(expected="expression didn't panic")] fn fails_without_panic() { assert_panics!(1 + 1); } #[test] #[should_panic(expected="panic message didn't include expected string")] fn fails_without_substring() { assert_panics!(panic!("{} {}", "This", "Message"), includes("That Message")) } #[test] #[should_panic(expected="panic message included disallowed string")] fn fails_with_substring() { assert_panics!(panic!("{} {}", "This", "Message"), excludes("Message")) } } #[test] fn fails_without_panic() { assert_panics!( assert_panics!(1 + 1), includes("assertion failed at"), includes("expression didn't panic"), includes("expression: 1 + 1"), includes("returned: 2") ); } #[test] fn fails_without_substring() { assert_panics!( assert_panics!( panic!("{} {}", "This", "Message"), includes("That Message") ), includes("assertion failed at"), excludes("expression didn't panic"), includes("panic message didn't include expected string"), includes("expression: panic!(\"{} {}\", \"This\", \"Message\")"), includes("message: \"This Message\""), includes("expected: \"That Message\""), ); } #[test] fn fails_with_substring() { assert_panics!( assert_panics!( panic!("{} {}", "This", "Message"), excludes("Message") ), includes("assertion failed at"), excludes("expression didn't panic"), includes("panic message included disallowed string"), includes("expression: panic!(\"{} {}\", \"This\", \"Message\")"), includes("message: \"This Message\""), includes("disallowed: \"Message\""), ); } #[test] fn string_closure() { assert_panics!(panic!("{}, {}!", "Hello", "World"), |msg| { assert_eq!(msg, "Hello, World!"); }) } #[test] fn str_closure() { assert_panics!(panic!("Hello, World!"), |msg| { assert_eq!(msg, "Hello, World!"); }) } #[test] fn str_closure_mismatch() { assert_panics!( assert_panics!(panic!(32), |_msg| { panic!("CUSTOM PANIC"); }), includes("assertion failed at"), includes("expression panic type wasn't String or &str"), excludes("CUSTOM PANIC") ) } #[test] fn str_closure_panics() { assert_panics!( assert_panics!(panic!("Hello, World!"), |_msg| { panic!("NOPE"); }), includes("NOPE"), excludes("Hello, World!"), ); } #[test] fn typed_closure() { assert_panics!(panic!(244 as i32), |value: &i32| { assert_eq!(value, &244); }) } #[test] fn typed_closure_mismatch() { assert_panics!( assert_panics!(panic!(244 as i32), |_value: &i64| { panic!("CUSTOM PANIC") }), excludes("CUSTOM PANIC"), includes("expression panic type mismatch"), includes("expression: panic!(244 as i32)"), includes("expected: i64"), ); } }