Add demo test screnarion

Author: bitbonk

src/GitVersion.Core.Tests/IntegrationTests/VersioningDemoScenario.cs

@@ -0,0 +1,112 @@
+using GitTools.Testing;
+using GitVersion.Model.Configuration;
+using GitVersion.OutputVariables;
+using LibGit2Sharp;
+using NUnit.Framework;
+using Shouldly;
+
+namespace GitVersion.Core.Tests.IntegrationTests;
+
+public class VersioningDemoScenario
+{
+    [Test]
+    public void ReleaseAndDevelopProblemDemo()
+    {
+        var configuration = new Config
+        {
+            // Settings the below NextVersion results in an exception
+            // I wanted to set it to globally start with version 1
+            // NextVersion = "1.0"
+        };
+
+        // create main and develop branch, develop is two commits ahead of main
+        using var fixture = new EmptyRepositoryFixture();
+        fixture.Repository.MakeACommit();
+        Commands.Checkout(fixture.Repository, fixture.Repository.CreateBranch("develop"));
+        fixture.Repository.MakeACommit();
+        fixture.Repository.MakeACommit();
+
+        var previousVersion = GetSemVer(fixture.GetVersion(configuration));
+
+        // make a 3rd commit on develop
+        fixture.Repository.MakeACommit();
+
+
+        var currentVersion = GetSemVer(fixture.GetVersion(configuration));
+
+        currentVersion.ShouldBeGreaterThan(previousVersion,
+            "the semver should be incremented after a commit on develop");
+
+        // we are ready to prepare the 1.0.0 release, create and checkout release/1.0.0
+        Commands.Checkout(fixture.Repository, fixture.Repository.CreateBranch("release/1.0.0"));
+
+        fixture.GetVersion(configuration).SemVer.ShouldBe("1.0.0-beta.1",
+            "the first semver on release/1.0.0 should be beta1");
+
+        // make another commit on release/1.0.0 to prepare the actual beta1 release
+        fixture.Repository.MakeACommit();
+
+        fixture.GetVersion(configuration).SemVer.ShouldBe("1.0.0-beta.1",
+            "the semver on release/1.0.0 should still be be beta1");
+
+        Commands.Checkout(fixture.Repository, fixture.Repository.Branches["develop"]);
+
+        previousVersion = currentVersion;
+        currentVersion = GetSemVer(fixture.GetVersion(configuration));
+
+        currentVersion.ShouldBe(previousVersion,
+            "the semver on develop should not have changed " +
+            "even when release/1.0.0 has new commits due to beta 1 preparations");
+
+        // now some other team member makes changes on develop that may or may not end up in 1.0.0
+        fixture.Repository.MakeACommit();
+        fixture.Repository.MakeACommit();
+
+        previousVersion = currentVersion;
+        currentVersion = GetSemVer(fixture.GetVersion(configuration));
+
+        currentVersion.ShouldBeGreaterThan(previousVersion,
+            "the semver should be incremented after a even more commit on develop");
+
+        Commands.Checkout(fixture.Repository, fixture.Repository.Branches["release/1.0.0"]);
+
+        // now we release the beta 1
+        fixture.Repository.ApplyTag("1.0.0-beta1");
+
+        fixture.GetVersion(configuration).SemVer.ShouldBe("1.0.0-beta.1",
+            "the on release/1.0.0 should still be beta1 after the beta 1 tag");
+
+        // continue with more work on develop that may or may not end up in 1.0.0
+        Commands.Checkout(fixture.Repository, fixture.Repository.Branches["develop"]);
+        fixture.Repository.MakeACommit();
+        fixture.Repository.MakeACommit();
+
+        previousVersion = currentVersion;
+        currentVersion = GetSemVer(fixture.GetVersion(configuration));
+
+        currentVersion.ShouldBeGreaterThan(previousVersion,
+            "the semver should be incremented after a even more commit on develop");
+
+        // now we decide that the three commits on develop should be part of the beta 2 release
+        // se we merge it into release/1.0.0 with --no-ff because it is a protected branch
+        Commands.Checkout(fixture.Repository, fixture.Repository.Branches["release/1.0.0"]);
+        fixture.Repository.Merge(
+            fixture.Repository.Branches["develop"],
+            Generate.SignatureNow(),
+            new MergeOptions {FastForwardStrategy = FastForwardStrategy.NoFastForward});
+
+        fixture.GetVersion(configuration).SemVer.ShouldBe("1.0.0-beta.2",
+            "the next semver on release/1.0.0 should be beta2");
+
+        Commands.Checkout(fixture.Repository, fixture.Repository.Branches["develop"]);
+        previousVersion = currentVersion;
+        currentVersion = GetSemVer(fixture.GetVersion(configuration));
+
+        currentVersion.ShouldBeGreaterThanOrEqualTo(previousVersion,
+            "the semver should be incremented (or unchanged) " +
+            "after we merged develop into release/1.0.0");
+
+        static SemanticVersion GetSemVer(VersionVariables ver)
+            => SemanticVersion.Parse(ver.FullSemVer, null);
+    }
+}