Is there a way to remove the first instance of an Object with specific key values from a list of Objects

The Dart/Flutter documentation mentions using remove and removeWhere as being the right way to remove objects from a list of objects.

This is also answered here on SO:

1. Dart Reference

> Removes the first occurrence of value from this list.
>
> Returns true if value was in the list, false otherwise. The list must
> be growable.

2. DevSheet Article

> If you want to delete a single item from the list with its first
> occurrence in the list then you can use the List.remove() function. It
> will search for the first occurrence of the item in the list and
> delete it. The remove() function takes the item as a parameter and
> deletes it.

3. StackOverflow Question

4. Flutter By Example

> remove(element) removes a single element from the list, which is
> strictly equal to the element passed in.

So I came up with the following code to try implement something I have in mind:

class Test {
  bool? a;
  bool? b;
  String? ex;
  String? yz;
  
  Test({
    this.a,
    this.b,
    this.ex,
    this.yz,
  });
  
   Map<String, dynamic> toJson() =>
      {
        "a": a,
        "b": b,
        "ex": ex,
        "yz": yz,
      
      };
  
  Test copy({bool? a, bool? b, String? ex, String? yz}){
    return Test(
      a : a ?? this.a,
      b : b ?? this.b,
      ex : ex ?? this.ex,
      yz : yz ?? this.yz,
    );
  }
  

}

void main() {
  Test a = Test(
    a : true,
    b : false,
    ex : "S001",
    yz : "plus"
  );
  
  Test b = Test(
    a : false,
    b : true,
    ex : "S001",
    yz : "plus"
  );
  
  Test c = Test(
    a : true,
    b : true,
    ex : "S001",
    yz : "plus"
  );
  
  Test d = Test(
    a : false,
    b : false,
    ex : "S001",
    yz : "plus"
  );
  
  Test z = a.copy(); // we want to remove an object with attributes matching 'a' from the list
  
  List<Test> testList = [a, b, c, d];
  
  for(var item in testList){ print(item.toJson()); } // [a, b, c, d]
  
  var result = testList.remove(z);
  
  print(result);
  
  for(var item in testList){ print(item.toJson()); }
  
}

However when I try to implement this, the remove function returns false.
My result is a false, and the object in question is not removed from the list.
While removing 'a' from the list works just fine, removing a.copy() doesn't.

Am I doing something wrong or is there a different way to remove said object from the list?

I've added this code to a public dartpad. Can anyone help me understand why this isn't working and what can be done to obtain the desired result?

Dartpad link

{a: true, b: false, ex: S001, yz: plus}
{a: false, b: true, ex: S001, yz: plus}
{a: true, b: true, ex: S001, yz: plus}
{a: false, b: false, ex: S001, yz: plus}
false
{a: true, b: false, ex: S001, yz: plus}
{a: false, b: true, ex: S001, yz: plus}
{a: true, b: true, ex: S001, yz: plus}
{a: false, b: false, ex: S001, yz: plus}

I looked around for the answer and apparently, I need to override the '==' operator and the hashCode functions so 'remove' can correctly compare two objects of the same class and remove the object from the list.

 @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    return other is Test &&
        other.a == a &&
        other.b == b &&
        other.ex == ex &&
        other.yz == yz;
  }
  
  @override
  int get hashCode => Object.hash(a, b, ex, yz);

Now the remove works. Uncommenting the line for 'z':

  Test z = a.copy(); 
  List<Test> testList = [a, b, c, d];
  for(var item in testList){ print(item.toJson()); } // [a, b, c, d]

  var result = testList.remove(z);  // works now
  // var result = testList.remove(a.copy()); // also works

  print(result); // true 
  for(var item in testList){ print(item.toJson()); }

yields the result:

{a: true, b: false, ex: S001, yz: plus}
{a: false, b: true, ex: S001, yz: plus}
{a: true, b: true, ex: S001, yz: plus}
{a: false, b: false, ex: S001, yz: plus}
true
{a: false, b: true, ex: S001, yz: plus}
{a: true, b: true, ex: S001, yz: plus}
{a: false, b: false, ex: S001, yz: plus}