[core] add tests for function parsing

test/style/conversion/function.test.cpp

@@ -0,0 +1,54 @@
+#include <mbgl/test/util.hpp>
+
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/rapidjson_conversion.hpp>
+#include <mbgl/style/conversion/constant.hpp>
+#include <mbgl/style/conversion/function.hpp>
+#include <mbgl/util/rapidjson.hpp>
+
+using namespace mbgl;
+using namespace mbgl::style;
+using namespace mbgl::style::conversion;
+
+auto parseFunction(const std::string& src) {
+    JSDocument doc;
+    doc.Parse<0>(src);
+    return convert<Function<float>>(doc);
+}
+
+TEST(StyleConversion, Function) {
+    auto fn1 = parseFunction("{\"stops\":[]}");
+    ASSERT_FALSE(fn1);
+    ASSERT_EQ("function must have at least one stop", fn1.error().message);
+
+    auto fn2 = parseFunction("{\"stops\":[1]}");
+    ASSERT_FALSE(fn2);
+    ASSERT_EQ("function stop must be an array", fn2.error().message);
+
+    auto fn3 = parseFunction("{\"stops\":[[]]}");
+    ASSERT_FALSE(fn3);
+    ASSERT_EQ("function stop must have two elements", fn3.error().message);
+
+    auto fn4 = parseFunction("{\"stops\":[[-1,-1]]}");
+    ASSERT_TRUE(bool(fn4));
+
+    auto fn5 = parseFunction("{\"stops\":[[0,1,2]]}");
+    ASSERT_FALSE(fn5);
+    ASSERT_EQ("function stop must have two elements", fn5.error().message);
+
+    auto fn6 = parseFunction("{\"stops\":[[0,\"x\"]]}");
+    ASSERT_FALSE(fn6);
+    ASSERT_EQ("value must be a number", fn6.error().message);
+
+    auto fn7 = parseFunction("{}");
+    ASSERT_FALSE(fn7);
+    ASSERT_EQ("function value must specify stops", fn7.error().message);
+
+    auto fn8 = parseFunction("[]");
+    ASSERT_FALSE(fn8);
+    ASSERT_EQ("function must be an object", fn8.error().message);
+
+    auto fn9 = parseFunction("{\"stops\":[[0,0]],\"base\":false}");
+    ASSERT_FALSE(fn9);
+    ASSERT_EQ("function base must be a number", fn9.error().message);
+}