always emit a small component view

Unit Tests for Reodering by Predicate

unit_tests/partition/reorder_first_last.cpp

@@ -0,0 +1,54 @@
+#include "partition/reorder_first_last.hpp"
+
+#include <boost/test/test_case_template.hpp>
+#include <boost/test/unit_test.hpp>
+
+#include <algorithm>
+#include <functional>
+#include <iterator>
+#include <utility>
+#include <vector>
+
+using namespace osrm::partition;
+
+BOOST_AUTO_TEST_SUITE(reorder_first_last)
+
+BOOST_AUTO_TEST_CASE(reordering_one_is_equivalent_to_min_and_max)
+{
+    std::vector<int> range{9, 0, 8, 1, 7, 2, 6, 3, 5, 4};
+
+    reorderFirstLast(begin(range), end(range), 1, std::less<>{});
+
+    BOOST_CHECK_EQUAL(range.front(), 0);
+    BOOST_CHECK_EQUAL(range.back(), 9);
+
+    reorderFirstLast(begin(range), end(range), 1, std::greater<>{});
+
+    BOOST_CHECK_EQUAL(range.front(), 9);
+    BOOST_CHECK_EQUAL(range.back(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(reordering_n_shuffles_n_smallest_to_front_n_largest_to_back)
+{
+    std::vector<int> range{9, 3, 8, 2};
+
+    reorderFirstLast(begin(range), end(range), 2, std::less<>{});
+
+    // Smallest at front, but: no ordering guarantee in that subrange!
+    BOOST_CHECK((range[0] == 2 and range[1] == 3) or (range[0] == 3 and range[1] == 2));
+
+    // Largest at back, but: no ordering guarantee in that subrange!
+    BOOST_CHECK((range[2] == 8 and range[3] == 9) or (range[2] == 9 and range[3] == 8));
+}
+
+BOOST_AUTO_TEST_CASE(reordering_n_with_iterators)
+{
+    std::vector<int> range{9, 3, 8, 2};
+
+    reorderFirstLast(begin(range), end(range), 1, std::less<>{});
+
+    BOOST_CHECK_EQUAL(range.front(), 2);
+    BOOST_CHECK_EQUAL(range.back(), 9);
+}
+
+BOOST_AUTO_TEST_SUITE_END()