Test "line intersects quad". Remove redundant test.

math/src/common.cpp

@@ -96,7 +96,7 @@ namespace math {
       return intersects(lhs, ln);
     };
     return std::any_of(segments.begin(), segments.end(), lhs_intersects) ||
-           contains(segments, lhs.first) || contains(segments, lhs.second);
+           contains(segments, lhs.first);
   }
 
   bool intersects(dim2::quad const & lhs, dim2::circle const & rhs) {

math/test/common_test.cxx

@@ -93,3 +93,32 @@ TEST_F(UnitSquareTest, PointOutsideSquare) {
 INSTANTIATE_TEST_CASE_P(Contains, UnitSquareTest,
                         Combine(ValuesIn(generate(0.f, 1.f, 0.25f)),
                                 ValuesIn(generate(0.f, 1.f, 0.25f))));
+
+struct LineQuadTest : TestWithParam<point> {};
+
+TEST_P(LineQuadTest, OriginLineIntersectsUnitSquare) {
+  square const unit{{{0, 0}}, 1};
+  line const ln{{{0, 0}}, GetParam()};
+  EXPECT_TRUE(math::intersects(ln, unit));
+}
+
+TEST_F(LineQuadTest, JustPointIntersection) {
+  square const unit{{{0, 0}}, 1};
+  line const ln{{{1, 1}}, {{2, 1}}};
+  EXPECT_TRUE(math::intersects(ln, unit));
+}
+
+TEST_F(LineQuadTest, EntirelyEncasedIntersection) {
+  square const unit{{{0, 0}}, 1};
+  line const ln{{{0.5, 0.5}}, {{0.75, 0.75}}};
+  EXPECT_TRUE(math::intersects(ln, unit));
+}
+
+TEST_F(LineQuadTest, OutsideByAnInch) {
+  square const unit{{{0, 0}}, 1};
+  line const ln{{{1.001, 1}}, {{2, 1}}};
+  math::intersects(ln, unit);
+  EXPECT_FALSE(math::intersects(ln, unit));
+}
+
+INSTANTIATE_TEST_CASE_P(Intersects, LineQuadTest, ValuesIn(line_ends));