BadImageFormatException - The signature is incorrect

IConsole.cs

public interface IConsole {
    void WriteLine(string line);
}

Test.cs

public class Test {
    [Fact]
    public void DoodadWritesToConsole() {
        // Arrange
        var thingyMock = new Mock<Thingy>();
        var doodad = new Doodad(thingyMock.Object);
        
        // Act
        doodad.DoAThing(writeToConsole: false);
      
        // Assert
        thingyMock.Verify(t => t.MakeConsole(), Times.Never());
    }
}

Thingy.cs

public class Thingy {
    public virtual IConsole MakeConsole() { return null; }
}