Add feature flagging tests.

src/Makefile.gtest.include

@@ -30,6 +30,7 @@ zcash_gtest_SOURCES += \
 	gtest/test_deprecation.cpp \
 	gtest/test_dynamicusage.cpp \
 	gtest/test_equihash.cpp \
+	gtest/test_feature_flagging.cpp \
 	gtest/test_history.cpp \
 	gtest/test_httprpc.cpp \
 	gtest/test_joinsplit.cpp \

src/gtest/test_feature_flagging.cpp

@@ -0,0 +1,97 @@
+#include <gtest/gtest.h>
+
+#include "chainparams.h"
+#include "consensus/params.h"
+#include "utiltest.h"
+
+#include <optional>
+
+enum TestFeature : uint32_t {
+    TF_1,
+    TF_2,
+    TF_3,
+    TF_4,
+    TF_MAX
+};
+
+struct TestParams {
+    std::set<TestFeature> vRequiredFeatures;
+
+    bool NetworkUpgradeActive(int nHeight, Consensus::UpgradeIndex idx) const {
+        switch (idx) {
+            case Consensus::BASE_SPROUT:
+                return nHeight >= 0;
+            case Consensus::UPGRADE_OVERWINTER:
+                return nHeight >= 5;
+            case Consensus::UPGRADE_SAPLING:
+                return nHeight >= 10;
+            case Consensus::UPGRADE_BLOSSOM:
+                return nHeight >= 15;
+            case Consensus::UPGRADE_HEARTWOOD:
+                return nHeight >= 20;
+            case Consensus::UPGRADE_CANOPY:
+                return nHeight >= 25;
+            case Consensus::UPGRADE_ZFUTURE:
+                return nHeight >= 30;
+            default:
+                return false;
+        }
+    }
+
+    bool FeatureRequired(const TestFeature feature) const {
+        return vRequiredFeatures.count(feature) > 0;
+    }
+};
+
+TEST(FeatureFlagging, FeatureDependencies) {
+    TestParams params;
+
+    Consensus::FeatureSet<TestFeature, TestParams> features({
+        {
+            .dependsOn = {},
+            .activation = Consensus::BASE_SPROUT
+        },
+        {
+            .dependsOn = {TF_1},
+            .activation = Consensus::UPGRADE_OVERWINTER
+        },
+        {
+            .dependsOn = {},
+            .activation = Consensus::UPGRADE_BLOSSOM
+        },
+        {
+            .dependsOn = {TF_2, TF_3},
+            .activation = Consensus::UPGRADE_HEARTWOOD
+        }
+    });
+
+    EXPECT_TRUE(features.FeatureActive(params, 1, TF_1));
+    EXPECT_FALSE(features.FeatureActive(params, 1, TF_2));
+    EXPECT_FALSE(features.FeatureActive(params, 1, TF_3));
+    EXPECT_FALSE(features.FeatureActive(params, 1, TF_4));
+
+    EXPECT_TRUE(features.FeatureActive(params, 5, TF_1));
+    EXPECT_TRUE(features.FeatureActive(params, 5, TF_2));
+    EXPECT_FALSE(features.FeatureActive(params, 5, TF_3));
+    EXPECT_FALSE(features.FeatureActive(params, 5, TF_4));
+
+    EXPECT_TRUE(features.FeatureActive(params, 15, TF_1));
+    EXPECT_TRUE(features.FeatureActive(params, 15, TF_2));
+    EXPECT_TRUE(features.FeatureActive(params, 15, TF_3));
+    EXPECT_FALSE(features.FeatureActive(params, 15, TF_4));
+
+    EXPECT_TRUE(features.FeatureActive(params, 20, TF_1));
+    EXPECT_TRUE(features.FeatureActive(params, 20, TF_2));
+    EXPECT_TRUE(features.FeatureActive(params, 20, TF_3));
+    EXPECT_TRUE(features.FeatureActive(params, 20, TF_4));
+
+    // Force TF_4 to be active
+    params.vRequiredFeatures.insert(TF_4);
+
+    // Ensure that a feature cannot be forced to be active if
+    // all of its dependencies are not active
+    EXPECT_DEATH(features.FeatureActive(params, 5, TF_4), "");
+    // A feature can be activated before its activation height
+    // if all of its dependencies are active
+    EXPECT_TRUE(features.FeatureActive(params, 15, TF_4));
+}