Add tests for lru-cache.hh

src/libutil/tests/lru-cache.cc

@@ -0,0 +1,130 @@
+#include "lru-cache.hh"
+#include <gtest/gtest.h>
+
+namespace nix {
+
+    /* ----------------------------------------------------------------------------
+     * size
+     * --------------------------------------------------------------------------*/
+
+    TEST(LRUCache, sizeOfEmptyCacheIsZero) {
+        LRUCache<std::string, std::string> c(10);
+        ASSERT_EQ(c.size(), 0);
+    }
+
+    TEST(LRUCache, sizeOfSingleElementCacheIsOne) {
+        LRUCache<std::string, std::string> c(10);
+        c.upsert("foo", "bar");
+        ASSERT_EQ(c.size(), 1);
+    }
+
+    /* ----------------------------------------------------------------------------
+     * upsert / get
+     * --------------------------------------------------------------------------*/
+
+    TEST(LRUCache, getFromEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        auto val = c.get("x");
+        ASSERT_EQ(val.has_value(), false);
+    }
+
+    TEST(LRUCache, getExistingValue) {
+        LRUCache<std::string, std::string> c(10);
+        c.upsert("foo", "bar");
+        auto val = c.get("foo");
+        ASSERT_EQ(val, "bar");
+    }
+
+    TEST(LRUCache, getNonExistingValueFromNonEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        c.upsert("foo", "bar");
+        auto val = c.get("another");
+        ASSERT_EQ(val.has_value(), false);
+    }
+
+    TEST(LRUCache, upsertOnZeroCapacityCache) {
+        LRUCache<std::string, std::string> c(0);
+        c.upsert("foo", "bar");
+        auto val = c.get("foo");
+        ASSERT_EQ(val.has_value(), false);
+    }
+
+    TEST(LRUCache, updateExistingValue) {
+        LRUCache<std::string, std::string> c(1);
+        c.upsert("foo", "bar");
+
+        auto val = c.get("foo");
+        ASSERT_EQ(val.value_or("error"), "bar");
+        ASSERT_EQ(c.size(), 1);
+
+        c.upsert("foo", "changed");
+        val = c.get("foo");
+        ASSERT_EQ(val.value_or("error"), "changed");
+        ASSERT_EQ(c.size(), 1);
+    }
+
+    TEST(LRUCache, overwriteOldestWhenCapacityIsReached) {
+        LRUCache<std::string, std::string> c(3);
+        c.upsert("one", "eins");
+        c.upsert("two", "zwei");
+        c.upsert("three", "drei");
+
+        ASSERT_EQ(c.size(), 3);
+        ASSERT_EQ(c.get("one").value_or("error"), "eins");
+
+        // exceed capacity
+        c.upsert("another", "whatever");
+
+        ASSERT_EQ(c.size(), 3);
+        // Retrieving "one" makes it the most recent element thus
+        // two will be the oldest one and thus replaced.
+        ASSERT_EQ(c.get("two").has_value(), false);
+        ASSERT_EQ(c.get("another").value(), "whatever");
+    }
+
+    /* ----------------------------------------------------------------------------
+     * clear
+     * --------------------------------------------------------------------------*/
+
+    TEST(LRUCache, clearEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        c.clear();
+        ASSERT_EQ(c.size(), 0);
+    }
+
+    TEST(LRUCache, clearNonEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        c.upsert("one", "eins");
+        c.upsert("two", "zwei");
+        c.upsert("three", "drei");
+        ASSERT_EQ(c.size(), 3);
+        c.clear();
+        ASSERT_EQ(c.size(), 0);
+    }
+
+    /* ----------------------------------------------------------------------------
+     * erase
+     * --------------------------------------------------------------------------*/
+
+    TEST(LRUCache, eraseFromEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        c.erase("foo");
+        ASSERT_EQ(c.size(), 0);
+    }
+
+    TEST(LRUCache, eraseMissingFromNonEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        c.upsert("one", "eins");
+        c.erase("foo");
+        ASSERT_EQ(c.size(), 1);
+        ASSERT_EQ(c.get("one").value_or("error"), "eins");
+    }
+
+    TEST(LRUCache, eraseFromNonEmptyCache) {
+        LRUCache<std::string, std::string> c(10);
+        c.upsert("one", "eins");
+        c.erase("one");
+        ASSERT_EQ(c.size(), 0);
+        ASSERT_EQ(c.get("one").value_or("empty"), "empty");
+    }
+}