Again with other SC:(Error: Returned error: VM Exception while processing transaction: revert) (Sorry but earlier problem did not solve)

Following are my contracts:

pragma solidity 0.5.16;
contract F1{
address public owner;
uint public bal= 1 ether;
constructor() public {
   owner = msg.sender;
function() external payable {
   bal = bal + msg.value;

== and my tester is:

pragma solidity ^0.5.16;
import "truffle/Assert.sol";
import "truffle/DeployedAddresses.sol";
import "../contracts/Funding.sol";

contract TestFunding {
  // Truffle will send the TestContract one Ether after deploying the contract.
  uint public initialBalance = 1 ether;

  function testInitialBalanceUsingDeployedContract() public {
    Funding funding = Funding(DeployedAddresses.Funding());

    // perform an action which sends value to myContract, then assert.
    Assert.equal(funding.bal(), 0, "Ether transferred");
    //Assert.equal(funding.bal, 0,"Ether  transferred");
    //Assert.equal(funding.bal(), 11,"Ether not transferred");

  function () external payable {
    // This will NOT be executed when Ether is sent. \o/


const F1 = artifacts.require("F1");

module.exports = function(deployer) {

I am getting following error during truffle test:

$ truffle test
Using network 'development'.

Compiling your contracts...
> Compiling ./contracts/F1.sol
> Compiling ./test/TestF1.sol
> Artifacts written to /tmp/test--13270-blknLiBqwAGU
> Compiled successfully using:
- solc: 0.5.16+commit.9c3226ce.Emscripten.clang
1) testInitialBalanceUsingDeployedContract
> No events were emitted

0 passing (6s)
1 failing
1) TestF1
Error: Returned error: VM Exception while processing transaction: revert
at Context.TestCase (/truffle/build/webpack:/packages/core/lib/testing/SolidityTest.js:92:1)
at process._tickCallback (internal/process/next_tick.js:68:7)
@lc2530hz:~/Truffle_programs/TransferEther2$ truffle version
Truffle v5.1.67 (core: 5.1.67)
Solidity v0.5.16 (solc-js)
Node v10.23.3
Web3.js v1.2.9

Somebody please guide me.