diff --git a/EconDataLens.Tests/DbReset.cs b/EconDataLens.Tests/DbReset.cs
index 2e4257e..cdbd294 100644
--- a/EconDataLens.Tests/DbReset.cs
+++ b/EconDataLens.Tests/DbReset.cs
@@ -1,8 +1,9 @@
 using EconDataLens.Data;
 using Microsoft.EntityFrameworkCore;
 
-[SetUpFixture]
-public class DbReset
+namespace EconDataLens.Tests;
+
+public static class DbReset
 {
     public static async Task RecreateDatabaseAsync(string connectionString)
     {
diff --git a/EconDataLens.Tests/EtlRepositoryTests/SeriesEtlRepositoryTests.cs b/EconDataLens.Tests/EtlRepositoryTests/SeriesEtlRepositoryTests.cs
new file mode 100644
index 0000000..a1ee69d
--- /dev/null
+++ b/EconDataLens.Tests/EtlRepositoryTests/SeriesEtlRepositoryTests.cs
@@ -0,0 +1,145 @@
+using EconDataLens.Core.Interfaces;
+using EconDataLens.Core.Configuration;
+using EconDataLens.Services;
+using EconDataLens.Data;
+using EconDataLens.Repositories;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Options;
+
+namespace EconDataLens.Tests.EtlRepositoryTests;
+
+public class SeriesEtlRepositoryTests
+{
+    private EconDataLensDbContext _dbContext = null!;
+    private ICpiDataFileParser _parser = null!;
+    private ICpiIngestionRepository _repository = null!;
+    private string _connectionString = string.Empty;
+
+    [SetUp]
+    public async Task SetUp()
+    {
+        _connectionString = PostgresFixture.ConnectionString;
+        var opts = new DbContextOptionsBuilder<EconDataLensDbContext>()
+            .UseNpgsql(_connectionString)
+            .UseSnakeCaseNamingConvention()
+            .Options;
+
+        await DbReset.RecreateDatabaseAsync(_connectionString);
+        
+
+        var blsOptions = Options.Create(new BlsOptions
+        {
+            Cpi = new CpiOptions
+            {
+                SeriesFile = "cu.series.sample"
+            }
+        });
+
+        var downloadOptions = Options.Create(new DownloadOptions
+        {
+            DownloadDirectory = "TestData/EtlData",
+            DeleteDownloadedFiles = false
+        });
+
+        _dbContext = new EconDataLensDbContext(opts);
+        _parser = new CpiDataFileParser(blsOptions, downloadOptions);
+        _repository = new CpiIngestionRepository(_dbContext);
+    }
+
+    [Test]
+    public async Task UpsertCpiSeriesAsync_NewSeries_InsertsSuccessfully()
+    {
+        var areaPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData", "cu.area.sample");
+        var itemPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData", "cu.item.sample");
+        var periodPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData",
+            "cu.period.sample");
+        var path = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData", "cu.series.sample");
+
+        // Load dependencies first
+        await _repository.UpsertCpiAreaAsync(_parser.ParseCpiAreasAsync(areaPath));
+        await _repository.UpsertCpiItemAsync(_parser.ParseCpiItemsAsync(itemPath));
+        await _repository.UpsertCpiPeriodAsync(_parser.ParseCpiPeriodsAsync(periodPath));
+        
+        // Now load series
+        await _repository.UpsertCpiSeriesAsync(_parser.ParseCpiSeriesAsync(path));
+
+        var count = await _dbContext.CpiSeries.CountAsync();
+
+        Assert.That(count, Is.EqualTo(8103));
+
+        var sample = await _dbContext.CpiSeries.FirstOrDefaultAsync(s => s.SeriesId == "CUSR0000SA0");
+
+        Assert.That(sample, Is.Not.Null);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(sample!.SeriesTitle, Is.EqualTo("All items in U.S. city average, all urban consumers, seasonally adjusted"));
+            Assert.That(sample!.AreaCode, Is.EqualTo("0000"));
+            Assert.That(sample!.ItemCode, Is.EqualTo("SA0"));
+            Assert.That(sample!.Seasonal, Is.EqualTo("S"));
+            Assert.That(sample!.PeriodicityCode, Is.EqualTo("R"));
+            Assert.That(sample!.BaseCode, Is.EqualTo("S"));
+            Assert.That(sample!.BasePeriod, Is.EqualTo("1982-84=100"));
+            Assert.That(sample!.FootnoteCodes, Is.Null);
+            Assert.That(sample!.BeginYear, Is.EqualTo(1947));
+            Assert.That(sample!.BeginPeriod, Is.EqualTo("M01"));
+            Assert.That(sample!.EndYear, Is.EqualTo(2025));
+            Assert.That(sample!.EndPeriod, Is.EqualTo("M08"));
+        });
+    }
+
+    [Test]
+    public async Task UpsertCpiSeriesAsync_ExistingSeries_UpdatesSuccessfully()
+    {
+        var areaPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData", "cu.area.sample");
+        var itemPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData", "cu.item.sample");
+        var periodPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData",
+            "cu.period.sample");
+        var path = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData", "cu.series.sample");
+        var modifiedPath = Path.Combine(TestContext.CurrentContext.TestDirectory, "TestData", "EtlData",
+            "cu.series.modified.sample");
+
+        // Load dependencies first
+        await _repository.UpsertCpiAreaAsync(_parser.ParseCpiAreasAsync(areaPath));
+        await _repository.UpsertCpiItemAsync(_parser.ParseCpiItemsAsync(itemPath));
+        await _repository.UpsertCpiPeriodAsync(_parser.ParseCpiPeriodsAsync(periodPath));
+        
+        // Now load series
+        await _repository.UpsertCpiSeriesAsync(_parser.ParseCpiSeriesAsync(path));
+
+        var count = await _dbContext.CpiSeries.CountAsync();
+
+        Assert.That(count, Is.EqualTo(8103));
+        
+        // Load modified series
+        await _repository.UpsertCpiSeriesAsync(_parser.ParseCpiSeriesAsync(modifiedPath));
+        
+        Assert.That(count, Is.EqualTo(8103));
+
+        var sample = await _dbContext.CpiSeries.FirstOrDefaultAsync(s => s.SeriesId == "CUSR0000SA0");
+
+        Assert.That(sample, Is.Not.Null);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(sample!.SeriesTitle, Is.EqualTo("modified"));
+            Assert.That(sample!.AreaCode, Is.EqualTo("0230"));
+            Assert.That(sample!.ItemCode, Is.EqualTo("SA0"));
+            Assert.That(sample!.Seasonal, Is.EqualTo("S"));
+            Assert.That(sample!.PeriodicityCode, Is.EqualTo("R"));
+            Assert.That(sample!.BaseCode, Is.EqualTo("S"));
+            Assert.That(sample!.BasePeriod, Is.EqualTo("1982-84=100"));
+            Assert.That(sample!.FootnoteCodes, Is.Null);
+            Assert.That(sample!.BeginYear, Is.EqualTo(1999));
+            Assert.That(sample!.BeginPeriod, Is.EqualTo("M01"));
+            Assert.That(sample!.EndYear, Is.EqualTo(2025));
+            Assert.That(sample!.EndPeriod, Is.EqualTo("M08"));
+        });
+    }
+
+    [TearDown]
+    public async Task TearDown()
+    {
+        await _dbContext.DisposeAsync();
+    }
+}
diff --git a/EconDataLens.Tests/TestData/EtlData/cu.series.modified.sample b/EconDataLens.Tests/TestData/EtlData/cu.series.modified.sample
new file mode 100644
index 0000000..0af554c
--- /dev/null
+++ b/EconDataLens.Tests/TestData/EtlData/cu.series.modified.sample
@@ -0,0 +1,2 @@
+series_id        	area_code	item_code	seasonal	periodicity_code	base_code	base_period	series_title	footnote_codes	begin_year	begin_period	end_year	end_period
+CUSR0000SA0      	0230	SA0	S	R	S	1982-84=100	modified		1999	M01	2025	M08