First draft of the interface.

test/Counter.t.sol

@@ -2,23 +2,5 @@
 pragma solidity ^0.8.13;
 
 import "forge-std/Test.sol";
-import "../src/Counter.sol";
 
-contract CounterTest is Test {
-    Counter public counter;
-
-    function setUp() public {
-        counter = new Counter();
-        counter.setNumber(0);
-    }
-
-    function testIncrement() public {
-        counter.increment();
-        assertEq(counter.number(), 1);
-    }
-
-    function testSetNumber(uint256 x) public {
-        counter.setNumber(x);
-        assertEq(counter.number(), x);
-    }
-}
+contract CounterTest is Test {}