1 // Copyright 2022 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 use crate::{
16 description::Description,
17 matcher::{Matcher, MatcherBase, MatcherResult},
18 };
19 use std::fmt::Debug;
20
21 /// Matches an empty container.
22 ///
23 /// `T` can be any container that implements `IntoIterator`. For instance, `T`
24 /// can be the reference of a common container like `&Vec` and
25 /// [`&HashSet`][std::collections::HashSet].
26 ///
27 /// ```
28 /// # use googletest::prelude::*;
29 /// # use std::collections::HashSet;
30 /// # fn should_pass() -> Result<()> {
31 /// let value: Vec<i32> = vec![];
32 /// verify_that!(value, empty())?;
33 /// let value: HashSet<i32> = HashSet::new();
34 /// verify_that!(value, empty())?;
35 /// let value: &[u32] = &[];
36 /// verify_that!(value, empty())?;
37 /// # Ok(())
38 /// # }
39 /// # should_pass().unwrap();
40 /// ```
empty() -> EmptyMatcher41 pub fn empty() -> EmptyMatcher {
42 EmptyMatcher
43 }
44
45 #[derive(MatcherBase)]
46 pub struct EmptyMatcher;
47
48 impl<T: Debug + Copy> Matcher<T> for EmptyMatcher
49 where
50 T: IntoIterator,
51 {
matches(&self, actual: T) -> MatcherResult52 fn matches(&self, actual: T) -> MatcherResult {
53 actual.into_iter().next().is_none().into()
54 }
55
describe(&self, matcher_result: MatcherResult) -> Description56 fn describe(&self, matcher_result: MatcherResult) -> Description {
57 if matcher_result.into() { "is empty" } else { "isn't empty" }.into()
58 }
59 }
60
61 #[cfg(test)]
62 mod tests {
63 use crate::prelude::*;
64 use std::collections::HashSet;
65
66 #[test]
empty_matcher_match_empty_vec() -> Result<()>67 fn empty_matcher_match_empty_vec() -> Result<()> {
68 let value: Vec<i32> = vec![];
69 verify_that!(value, empty())
70 }
71
72 #[test]
empty_matcher_does_not_match_empty_vec() -> Result<()>73 fn empty_matcher_does_not_match_empty_vec() -> Result<()> {
74 let value = vec![1, 2, 3];
75 verify_that!(value, not(empty()))
76 }
77
78 #[test]
empty_matcher_matches_empty_slice() -> Result<()>79 fn empty_matcher_matches_empty_slice() -> Result<()> {
80 let value: &[i32] = &[];
81 verify_that!(value, empty())
82 }
83
84 #[test]
empty_matcher_matches_empty_hash_set() -> Result<()>85 fn empty_matcher_matches_empty_hash_set() -> Result<()> {
86 let value: HashSet<i32> = HashSet::new();
87 verify_that!(value, empty())
88 }
89 }
90