1 files changed, 123 insertions, 0 deletions
diff --git a/test/style/property_expression.test.cpp b/test/style/property_expression.test.cpp
new file mode 100644
index 0000000000..e4ee5f115f
--- /dev/null
+++ b/test/style/property_expression.test.cpp
@@ -0,0 +1,123 @@
+#include <mbgl/test/util.hpp>
+#include <mbgl/test/stub_geometry_tile_feature.hpp>
+
+#include <mbgl/style/property_expression.hpp>
+#include <mbgl/renderer/property_evaluator.hpp>
+#include <mbgl/renderer/property_evaluation_parameters.hpp>
+#include <mbgl/style/expression/dsl.hpp>
+
+using namespace mbgl;
+using namespace mbgl::style;
+using namespace mbgl::style::expression::dsl;
+
+using namespace std::string_literals;
+
+static StubGeometryTileFeature oneInteger {
+    PropertyMap {{ "property", uint64_t(1) }}
+};
+
+static StubGeometryTileFeature oneDouble {
+    PropertyMap {{ "property", 1.0 }}
+};
+
+static StubGeometryTileFeature oneString {
+    PropertyMap {{ "property", "1"s }}
+};
+
+float evaluate(PropertyValue<float> value, float zoom) {
+    return value.evaluate(PropertyEvaluator<float>(PropertyEvaluationParameters(zoom), 0));
+}
+
+TEST(PropertyExpression, Constant) {
+    EXPECT_EQ(2.0f, evaluate(PropertyValue<float>(2.0), 0));
+    EXPECT_EQ(3.8f, evaluate(PropertyValue<float>(3.8), 0));
+    EXPECT_EQ(22.0f, evaluate(PropertyValue<float>(22.0), 0));
+    EXPECT_EQ(2.0f, evaluate(PropertyValue<float>(2.0), 4));
+    EXPECT_EQ(3.8f, evaluate(PropertyValue<float>(3.8), 4));
+    EXPECT_EQ(22.0f, evaluate(PropertyValue<float>(22.0), 4));
+    EXPECT_EQ(2.0f, evaluate(PropertyValue<float>(2.0), 22));
+    EXPECT_EQ(3.8f, evaluate(PropertyValue<float>(3.8), 22));
+    EXPECT_EQ(22.0f, evaluate(PropertyValue<float>(22.0), 22));
+}
+
+TEST(PropertyExpression, Expression) {
+    PropertyExpression<float> expression(interpolate(linear(), zoom(), 0.0, literal(0.0), 1.0, literal(1.0)));
+    EXPECT_EQ(0.0, evaluate(expression, 0.0));
+    EXPECT_EQ(0.5, evaluate(expression, 0.5));
+}
+
+TEST(PropertyExpression, Defaults) {
+    EXPECT_EQ(1.0f, PropertyExpression<float>(number(get("property")), 0.0)
+        .evaluate(oneInteger, 2.0f));
+    EXPECT_EQ(1.0f, PropertyExpression<float>(number(get("property")), 0.0)
+        .evaluate(oneDouble, 2.0f));
+    EXPECT_EQ(0.0f, PropertyExpression<float>(number(get("property")), 0.0)
+        .evaluate(oneString, 2.0f));
+    EXPECT_EQ(2.0f, PropertyExpression<float>(number(get("property")))
+        .evaluate(oneString, 2.0f));
+}
+
+TEST(PropertyExpression, ZoomInterpolation) {
+    EXPECT_EQ(40.0f, PropertyExpression<float>(
+        interpolate(linear(), zoom(),
+            0.0, interpolate(linear(), number(get("property")), 1.0, literal(24.0)),
+            1.5, interpolate(linear(), number(get("property")), 1.0, literal(36.0)),
+            3.0, interpolate(linear(), number(get("property")), 1.0, literal(48.0))
+        ), 0.0f)
+    .evaluate(2.0f, oneInteger, -1.0f)) << "Should interpolate between stops";
+    
+    EXPECT_EQ(33.0, PropertyExpression<float>(
+        interpolate(linear(), zoom(),
+            5.0, interpolate(linear(), number(get("property")), 1.0, literal(33.0)),
+            10.0, interpolate(linear(), number(get("property")), 1.0, literal(66.0))
+        ), 0.0f)
+    .evaluate(0.0f, oneInteger, -1.0f)) << "Use first stop output for input values from -inf to first stop";
+    
+    EXPECT_EQ(66.0, PropertyExpression<float>(
+        interpolate(linear(), zoom(),
+            0.0, interpolate(linear(), number(get("property")), 1.0, literal(33.0)),
+            10.0, interpolate(linear(), number(get("property")), 1.0, literal(66.0))
+        ), 0.0f)
+    .evaluate(20.0f, oneInteger, -1.0f)) << "Use last stop output for input values from last stop to +inf";
+
+    EXPECT_EQ(66.0f, PropertyExpression<float>(
+        interpolate(linear(), zoom(),
+            0.0, interpolate(linear(), number(get("property")), 1.0, literal(33.0)),
+            10.0, interpolate(linear(), number(get("property")), 1.0, literal(66.0))
+        ), 0.0f)
+    .evaluate(10.0f, oneInteger, -1.0f)) << "Should interpolate TO the last stop.";
+    
+    EXPECT_EQ(33.0f, PropertyExpression<float>(
+        interpolate(linear(), zoom(),
+            0.0, interpolate(linear(), number(get("property")), 1.0, literal(33.0)),
+            10.0, interpolate(linear(), number(get("property")), 1.0, literal(66.0))
+        ), 0.0f)
+    .evaluate(0.0f, oneInteger, -1.0f)) << "Should interpolate TO the first stop";
+}
+
+TEST(PropertyExpression, Issue8460) {
+    PropertyExpression<float> fn1(
+        interpolate(linear(), zoom(),
+            15.0, interpolate(linear(), number(get("property")), 1.0, literal(0.0)),
+            15.2, interpolate(linear(), number(get("property")), 1.0, literal(600.0))
+        ), 0.0f);
+
+    EXPECT_NEAR(  0.0f, fn1.evaluate(15.0f, oneInteger, -1.0f), 0.00);
+    EXPECT_NEAR(300.0f, fn1.evaluate(15.1f, oneInteger, -1.0f), 0.01);
+    EXPECT_NEAR(600.0f, fn1.evaluate(15.2f, oneInteger, -1.0f), 0.00);
+    EXPECT_NEAR(600.0f, fn1.evaluate(16.0f, oneInteger, -1.0f), 0.00);
+
+    PropertyExpression<float> fn2(
+        interpolate(linear(), zoom(),
+            15.0, interpolate(linear(), number(get("property")), 1.0, literal(0.0)),
+            15.2, interpolate(linear(), number(get("property")), 1.0, literal(300.0)),
+            18.0, interpolate(linear(), number(get("property")), 1.0, literal(600.0))
+        ), 0.0f);
+
+    EXPECT_NEAR(  0.0f, fn2.evaluate(15.0f, oneInteger, -1.0f), 0.00);
+    EXPECT_NEAR(150.0f, fn2.evaluate(15.1f, oneInteger, -1.0f), 0.01);
+    EXPECT_NEAR(300.0f, fn2.evaluate(15.2f, oneInteger, -1.0f), 0.00);
+    EXPECT_NEAR(385.71f, fn2.evaluate(16.0f, oneInteger, -1.0f), 0.01);
+    EXPECT_NEAR(600.0f, fn2.evaluate(18.0f, oneInteger, -1.0f), 0.00);
+    EXPECT_NEAR(600.0f, fn2.evaluate(19.0f, oneInteger, -1.0f), 0.00);
+}