nix/tests/unit/libutil/lru-cache.cc

#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);
        ASSERT_EQ(c.erase("foo"), false);
        ASSERT_EQ(c.size(), 0);
    }

    TEST(LRUCache, eraseMissingFromNonEmptyCache) {
        LRUCache<std::string, std::string> c(10);
        c.upsert("one", "eins");
        ASSERT_EQ(c.erase("foo"), false);
        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");
        ASSERT_EQ(c.erase("one"), true);
        ASSERT_EQ(c.size(), 0);
        ASSERT_EQ(c.get("one").value_or("empty"), "empty");
    }
}