contains_matches macro and more tests

backend/test_utils/src/contains_matches.rs

@@ -0,0 +1,94 @@
+/**
+This macro checks to see whether an iterable container contains each of the
+match items given, in the order that they are given in (but not necessarily
+contiguous, ie other items may be interspersed between the ones we're looking
+to match).
+
+Similar to `matches!`.
+
+```
+enum Item {
+    Foo { a: usize },
+    Bar(bool),
+    Wibble
+}
+
+use Item::*;
+
+let does_contain: bool = test_utils::contains_matches!(
+    vec![Foo { a: 2 }, Wibble, Bar(true), Foo { a: 100 }],
+    Foo { a: 2 } | Foo { a: 3 },
+    Bar(true),
+    Foo {..}
+);
+
+assert!(does_contain);
+```
+*/
+#[macro_export]
+macro_rules! contains_matches {
+    ($expression:expr, $( $( $pattern:pat )|+ $( if $guard:expr )? ),+ $(,)?) => {{
+        let mut items = $expression.into_iter();
+
+        // For each pattern we want to match, we consume items until
+        // we find the first match, and then break the loop and do the
+        // same again with the next pattern. If we run out of items, we
+        // set the validity to false and stop trying to match. Else, we
+        // match againse each of the patterns and return true.
+        let mut is_valid = true;
+        $(
+            while is_valid {
+                let item = match items.next() {
+                    Some(item) => item,
+                    None => {
+                        is_valid = false;
+                        break;
+                    }
+                };
+
+                match item {
+                    $( $pattern )|+ $( if $guard )? => break,
+                    _ => continue
+                }
+            }
+        )+
+
+        is_valid
+    }}
+}
+
+/**
+This macro checks to see whether an iterable container contains each of the
+match items given, in the order that they are given in (but not necessarily
+contiguous, ie other items may be interspersed between the ones we're looking
+to match).
+
+Panics if this is not the case.
+```
+enum Item {
+    Foo { a: usize },
+    Bar(bool),
+    Wibble
+}
+
+use Item::*;
+
+test_utils::assert_contains_matches!(
+    vec![Foo { a: 2 }, Wibble, Bar(true), Foo { a: 100 }],
+    Foo { a: 2 },
+    Bar(true),
+    Foo {..}
+);
+```
+*/
+#[macro_export]
+macro_rules! assert_contains_matches {
+    ($expression:expr, $( $( $pattern:pat )|+ $( if $guard:expr )? ),+ $(,)?) => {
+        let does_contain_matches = $crate::contains_matches!(
+            $expression,
+            $( $( $pattern )|+ $( if $guard )? ),+
+        );
+
+        assert!(does_contain_matches);
+    }
+}