docs: document mstore test

stack_ops_test.go

@@ -37,22 +37,23 @@ func TestMStore(t *testing.T) {
 	op := func(evm IEVM) error { return evm.MStore() }
 
 	// Stack
+	// [32, 444, 2, 3]
 	offset := 32
 	initialStack := []uint64{3, 2, 444, uint64(offset)}
 
 	// Memory
+	// Each word is represented by 32 bytes.
+	// [111, 222, 333]
 	word1 := uint256.NewInt(111).Bytes32()
 	word2 := uint256.NewInt(222).Bytes32()
 	word3 := uint256.NewInt(333).Bytes32()
 	var memory []byte
 	memory = append(append(append(memory, word1[:]...), word2[:]...), word3[:]...)
 
 	// Expected
+	// - Stack: [2, 3]
+	// - Memory: [111, 444, 333]
 	expectedStack := []uint64{3, 2}
-	var expectedMemory []byte
-	newWord := uint256.NewInt(444).Bytes32()
-	expectedMemory = append(append(append(expectedMemory, word1[:]...), newWord[:]...), word3[:]...)
-
 	testStackOperationWithNewEVM(t, op, nil, initialStack, expectedStack, memory, nil)
 }