add(tests): test cases for displayExpression

tests/CMakeLists.txt

@@ -1,8 +1,8 @@
-add_executable(metricq-combinator.test_single_derivation test_single_derivation.cpp)
-add_test(metricq-combinator.test_single_derivation metricq-combinator.test_single_derivation)
+macro(add_test_case test_name)
+  add_executable(${test_name} ${test_name}.cpp)
+  add_test(${test_name} ${test_name})
+  target_link_libraries(${test_name} PRIVATE metricq-combinator-lib)
+endmacro()
 
-target_link_libraries(
-    metricq-combinator.test_single_derivation
-    PRIVATE
-        metricq-combinator-lib
-)
+add_test_case(test_single_derivation)
+add_test_case(test_display_expression)

tests/test_display_expression.cpp

@@ -0,0 +1,69 @@
+#include "../src/combinator.hpp"
+#include <iostream>
+#include <metricq/json.hpp>
+
+int main()
+{
+    try
+    {
+        // Input test data
+        nlohmann::json data = {
+            { "testCases",
+              { { { "expression",
+                    { { "operation", "*" },
+                      { "left", 5 },
+                      { "right", { { "operation", "-" }, { "left", 45 }, { "right", 3 } } } } } },
+                { { "expression",
+                    { { "operation", "*" },
+                      { "left", { { "operation", "+" }, { "left", 1 }, { "right", 2 } } },
+                      { "right",
+                        { { "operation", "-" },
+                          { "left", 10 },
+                          { "right", "dummy.source" } } } } } },
+                { { "expression",
+                    { { "operation", "-" },
+                      { "left",
+                        { { "operation", "+" },
+                          { "left", 15.3 },
+                          { "right",
+                            { { "operation", "min" }, { "inputs", { 42, 24, 8, 12 } } } } } },
+                      { "right",
+                        { { "operation", "throttle" },
+                          { "cooldown_period", "42" },
+                          { "input", 8 } } } } } } } }
+        };
+
+        // Expected outputs
+        std::vector<std::string> expected = { "(5 * (45 - 3))", "((1 + 2) * (10 - dummy.source))",
+                                              "((15.300000 + min[42, 24, 8, 12]) - 8)" };
+
+        // Test the cases
+        const auto& testCases = data["testCases"];
+        for (size_t i = 0; i < testCases.size(); ++i)
+        {
+            const auto& testCase = testCases[i];
+            const auto& expression = testCase["expression"];
+
+            // Call the function to display the expression
+            std::string result = Combinator::displayExpression(expression);
+
+            // Compare with expected result
+            if (result != expected[i])
+            {
+                std::cerr << "Test case " << i + 1 << " failed:\n";
+                std::cerr << "Expected: " << expected[i] << "\n";
+                std::cerr << "Got: " << result << "\n";
+                return 1;
+            }
+        }
+
+        std::cout << "All test cases passed successfully!" << std::endl;
+    }
+    catch (const std::exception& e)
+    {
+        std::cerr << "Error: " << e.what() << std::endl;
+        return 1;
+    }
+
+    return 0;
+}