1 files changed, 75 insertions, 0 deletions
diff --git a/test/style/functions.test.cpp b/test/style/functions.test.cpp
new file mode 100644
index 0000000000..9577bcc633
--- /dev/null
+++ b/test/style/functions.test.cpp
@@ -0,0 +1,75 @@
+#include <iostream>
+#include <mbgl/test/util.hpp>
+
+#include <mbgl/style/property_evaluator.hpp>
+#include <mbgl/style/calculation_parameters.hpp>
+
+using namespace mbgl;
+using namespace mbgl::style;
+
+float evaluate(PropertyValue<float> value, float zoom) {
+    return PropertyValue<float>::visit(value, PropertyEvaluator<float>(CalculationParameters(zoom), 0));
+}
+std::string evaluate(PropertyValue<std::string> value, float zoom) {
+    return PropertyValue<std::string>::visit(value, PropertyEvaluator<std::string>(CalculationParameters(zoom), ""));
+}
+
+TEST(Function, Constant) {
+    EXPECT_EQ(2.0f, evaluate(2, 0));
+    EXPECT_EQ(3.8f, evaluate(3.8, 0));
+    EXPECT_EQ(22.0f, evaluate(22, 0));
+    EXPECT_EQ(2.0f, evaluate(2, 4));
+    EXPECT_EQ(3.8f, evaluate(3.8, 4));
+    EXPECT_EQ(22.0f, evaluate(22, 4));
+    EXPECT_EQ(2.0f, evaluate(2, 22));
+    EXPECT_EQ(3.8f, evaluate(3.8, 22));
+    EXPECT_EQ(22.0f, evaluate(22, 22));
+}
+
+TEST(Function, Stops) {
+    // Explicit constant slope in fringe regions.
+    Function<float> slope_1({ { 0, 1.5 }, { 6, 1.5 }, { 8, 3 }, { 22, 3 } }, 1.75);
+    EXPECT_EQ(1.5, evaluate(slope_1, 0));
+    EXPECT_EQ(1.5, evaluate(slope_1, 4));
+    EXPECT_EQ(1.5, evaluate(slope_1, 6));
+    ASSERT_FLOAT_EQ(2.0454545454545454, evaluate(slope_1, 7));
+    EXPECT_EQ(3.0, evaluate(slope_1, 8));
+    EXPECT_EQ(3.0, evaluate(slope_1, 9));
+    EXPECT_EQ(3.0, evaluate(slope_1, 15));
+    EXPECT_EQ(3.0, evaluate(slope_1, 22));
+
+
+    // Test constant values in fringe regions.
+    Function<float> slope_2({ { 6, 1.5 }, { 8, 3 } }, 1.75);
+    EXPECT_EQ(1.5, evaluate(slope_2, 0));
+    EXPECT_EQ(1.5, evaluate(slope_2, 4));
+    EXPECT_EQ(1.5, evaluate(slope_2, 6));
+    ASSERT_FLOAT_EQ(2.0454545454545454, evaluate(slope_2, 7));
+    EXPECT_EQ(3.0, evaluate(slope_2, 8));
+    EXPECT_EQ(3.0, evaluate(slope_2, 9));
+    EXPECT_EQ(3.0, evaluate(slope_2, 15));
+    EXPECT_EQ(3.0, evaluate(slope_2, 22));
+
+    // Test no values.
+    Function<float> slope_3({}, 1.75);
+    EXPECT_EQ(1, evaluate(slope_3, 2));
+    EXPECT_EQ(1, evaluate(slope_3, 6));
+    EXPECT_EQ(1, evaluate(slope_3, 12));
+
+
+    // Explicit constant slope in fringe regions.
+    Function<float> slope_4({ { 0, 2 }, { 8, 10 } }, 1);
+    EXPECT_EQ(2, evaluate(slope_4, 0));
+    EXPECT_EQ(3, evaluate(slope_4, 1));
+    EXPECT_EQ(4, evaluate(slope_4, 2));
+    EXPECT_EQ(4.75, evaluate(slope_4, 2.75));
+    EXPECT_EQ(10, evaluate(slope_4, 8));
+
+    // discrete values
+    Function<std::string> discrete_0({{ 3, "string0"}, {6, "string1"}, {9, "string2"}}, 1);
+    EXPECT_EQ("string0", evaluate(discrete_0, 2));
+    EXPECT_EQ("string0", evaluate(discrete_0, 4));
+    EXPECT_EQ("string1", evaluate(discrete_0, 7));
+    EXPECT_EQ("string2", evaluate(discrete_0, 9));
+    EXPECT_EQ("string2", evaluate(discrete_0, 10));
+}