It is more convenient than string.Format and you can use intellisense here too.
And here is my test method:
[TestMethod]
public void StringMethodsTest_DollarSign()
{
string name = "Forrest";
string surname = "Gump";
int year = 3;
string sDollarSign = $"My name is {name} {surname} and once I run more than {year} years.";
string expectedResult = "My name is Forrest Gump and once I run more than 3 years.";
Assert.AreEqual(expectedResult, sDollarSign);
}