Increased tests coverage

tests/detectors/external-function/0.4.25/external_function_3.sol

@@ -2,9 +2,7 @@ contract Test {
 
     function good(bytes x) external {}
     function good2() public {}
-
     function good3(uint256 x, uint256 y) public {}
-
     function good4(uint256[] x, string y) external {}
 
 }

tests/detectors/external-function/0.5.16/external_function_3.sol

@@ -1,10 +1,16 @@
+pragma experimental ABIEncoderV2;
+
 contract Test {
 
+    struct testStruct {
+        uint256 id;
+        string name;
+    }
+
     function good(bytes calldata x) external {}
     function good2() public {}
-
     function good3(uint256 x, uint256 y) public {}
-
     function good4(uint256[] calldata x, string calldata y) external {}
+    function good5(testStruct calldata x) external {}
 
 }

tests/detectors/external-function/0.6.11/external_function_3.sol

@@ -1,10 +1,16 @@
+pragma experimental ABIEncoderV2;
+
 contract Test {
 
+    struct testStruct {
+        uint256 id;
+        string name;
+    }
+
     function good(bytes calldata x) external {}
     function good2() public {}
-
     function good3(uint256 x, uint256 y) public {}
-
     function good4(uint256[] calldata x, string calldata y) external {}
+    function good5(testStruct calldata x) external {}
 
 }

tests/detectors/external-function/0.7.6/external_function_3.sol

@@ -1,10 +1,16 @@
+pragma experimental ABIEncoderV2;
+
 contract Test {
 
+    struct testStruct {
+        uint256 id;
+        string name;
+    }
+
     function good(bytes calldata x) external {}
     function good2() public {}
-
     function good3(uint256 x, uint256 y) public {}
-
     function good4(uint256[] calldata x, string calldata y) external {}
+    function good5(testStruct calldata x) external {}
 
 }