Add NewestReplica equality tests and gmock matcher for distinct elements in a range

Add a new `matchers` directory in vespalib which can be used as a repository for
generic, reusable GMock matchers.

Move distributor tests from using an explicit gtest runner to using `GTest::gmock_main`
which serves the same purpose. Need to depend on a gmock target (not just gtest) to
be able to link with stuff required for matchers.

1 files changed, 35 insertions, 0 deletions

diff --git a/vespalib/src/vespa/vespalib/gtest/matchers/elements_are_distinct.h b/vespalib/src/vespa/vespalib/gtest/matchers/elements_are_distinct.h
new file mode 100644
index 00000000000..374dafbf893
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/gtest/matchers/elements_are_distinct.h
@@ -0,0 +1,35 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+#include <ranges>
+
+/**
+ * Checks that all elements of a forward iterable range are distinct, i.e. the following must hold:
+ *   - for any single element `foo`, foo == foo is true
+ *   - for any two separate elements `foo` and `bar`, foo == bar is false
+ */
+MATCHER(ElementsAreDistinct, "") {
+    const auto& range = arg;
+    static_assert(std::ranges::forward_range<decltype(range)>);
+    const auto end = std::ranges::cend(range);
+    // Explicitly count element positions instead of comparing iterators to avoid depending
+    // on iterators being comparable with each other.
+    size_t i = 0;
+    for (auto lhs = std::ranges::cbegin(range); lhs != end; ++lhs, ++i) {
+        size_t j = 0;
+        for (auto rhs = std::ranges::cbegin(range); rhs != end; ++rhs, ++j) {
+            if (i != j) {
+                if (*lhs == *rhs) {
+                    *result_listener << "Expected elements to be distinct, but element at position "
+                                     << i << " (" << *lhs << ") is equal to element at position "
+                                     << j << " (" << *rhs << ")";
+                    return false;
+                }
+            } else if (!(*lhs == *rhs)) {
+                *result_listener << "Element at position " << i << " (" << *lhs << ") does not equal itself";
+                return false;
+            }
+        }
+    }
+    return true;
+}