
using Xunit;
namespace ConsoleApp {
    public class ProgramTests {
        [Fact(DisplayName = "CollectUniqueEmails returns only unique emails")] 
        public void CollectUniqueEmails_ReturnsUniqueEmails() {
            var input = new List<string> {
                "a@x.com", "b@y.com", "a@x.com", "c@z.com", "b@y.com"
            };
            var expected = new HashSet<string> {
                "a@x.com", "b@y.com", "c@z.com"
            };
            var result = Program.CollectUniqueEmails(input);
            Assert.Equal(expected.Count, result.Count);
            foreach (var email in expected) {
                Assert.Contains(email, result);
            }
        }

        [Fact(DisplayName = "CollectUniqueEmails handles all duplicates correctly")]
        public void CollectUniqueEmails_HandlesAllDuplicates() {
            var input = new List<string> {
                "repeat@a.com", "repeat@a.com", "repeat@a.com"
            };
            var expected = new HashSet<string> { "repeat@a.com" };
            var result = Program.CollectUniqueEmails(input);
            Assert.Single(result);
            Assert.Contains("repeat@a.com", result);
        }

        [Fact(DisplayName = "CollectUniqueEmails returns empty set for empty input")]
        public void CollectUniqueEmails_EmptyListReturnsEmptySet() {
            var input = new List<string>();
            var result = Program.CollectUniqueEmails(input);
            Assert.Empty(result);
        }
    }
}

ProgramTests.cs

Master the essential C# collections, from basic lists to advanced dictionaries and sets. This course blends engaging theory with practical, real-world challenges to help you confidently use collections in your C# projects.

Explore the foundational C# collections: arrays and lists. Learn how to create, manipulate, and apply them to solve practical problems.

Delve into C# dictionaries and related collections for efficient key-based data storage and retrieval.

Discover C# sets and useful collection utilities for advanced data manipulation and analysis.

Challenge: Unique Email Collector

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