chore(big): rewrite SBig tests to be black box tests

test/BigTest.hpp

@@ -1,5 +1,6 @@
 #include "Test.hpp"
 #include "storm/Big.hpp"
+#include <vector>
 
 class BigData;
 
@@ -15,4 +16,30 @@ struct BigDataTest {
     BigData** operator &() { return &num; }
     operator BigDataPtr() const { return num; }
     BigData* operator->() const { return num; }
+
+    uint32_t ToUnsigned() {
+        uint32_t result;
+        SBigToUnsigned(num, &result);
+        return result;
+    }
+
+    uint32_t BitLen() {
+        // Work around a SBigBitLen crash on 0 (original behavior)
+        if (SBigIsZero(num)) return 0;
+
+        uint32_t result = 0;
+        SBigBitLen(num, &result);
+        return result;
+    }
+
+    std::vector<uint8_t> ToBinaryBuffer() {
+        uint32_t size = (this->BitLen() + 32) / 8;
+        std::vector<uint8_t> data(size);
+
+        uint32_t bytes = 0;
+        SBigToBinaryBuffer(this->num, data.data(), size, &bytes);
+        data.resize(bytes);
+
+        return data;
+    }
 };