db-subclass-to-dto/tests/BeforeAfter.Tests/ExtractMethod/ReportTests.cs

using ExtractMethod.Tooling;
using Microsoft.CodeAnalysis;

namespace BeforeAfter.Tests.ExtractMethod;

/// <summary>
/// Tests for yak em 03: the signature promotion (SignatureBuilder) and the
/// formatted report (ReportFormatter) over the checked-in Demo.cs fixture.
/// Line anchors are the exact fixture lines pinned by em 01/02: ScoreReads
/// body 56..58, Summarize 68..76 (partial selection 68..72), Heaviest 87..93.
/// </summary>
public class ReportTests
{
    // ---------------------------------------------------------------------
    // Signature promotion, the case em 02's comment promises: in Summarize
    // lines 68..72, `total` sits in params[ref] AND returns (declared inside,
    // reassigned inside, read after), and `i` sits in params AND locals (the
    // for-header declares it inside). Promotion: both drop out of the params,
    // total becomes the plain return value -> `int Extract(int limit)`.
    // ---------------------------------------------------------------------
    [Fact]
    public void Signature_for_Summarize_selection_promotes_declared_inside_variables()
    {
        var (report, formatted) = Compose(68, 72);

        Assert.Equal(new[] { "limit" }, report.Signature.Params.Select(p => p.Name));
        Assert.Equal("int", report.Signature.ReturnType);
        Assert.Contains("suggested signature: int Extract(int limit)", formatted);
    }

    // ---------------------------------------------------------------------
    // Heaviest full body: `best` (declared inside, ref in the raw params,
    // trailing return candidate) promotes to the return; the for-var `i`
    // drops from the params; widgets/count stay as plain in-params.
    // ---------------------------------------------------------------------
    [Fact]
    public void Signature_for_Heaviest_returns_the_trailing_candidate_and_drops_declared_inside_params()
    {
        var (_, formatted) = Compose(87, 93);

        // Parameter order follows the classifier's ordinal-by-name order —
        // the same order the params bucket above prints (em 02 determinism).
        Assert.Contains("suggested signature: Widget Extract(int count, List<Widget> widgets)", formatted);
    }

    // ---------------------------------------------------------------------
    // No nameable return -> void (ScoreReads ends with `return score + bonus;`,
    // a composite expression v1 cannot name — the report notes this); locals
    // declared inside (seed, score) drop from the params; only the enclosing
    // method's own parameter survives.
    // ---------------------------------------------------------------------
    [Fact]
    public void Signature_for_ScoreReads_is_void_and_carries_only_the_enclosing_parameter()
    {
        var (report, formatted) = Compose(56, 58);

        Assert.Equal(new[] { "bonus" }, report.Signature.Params.Select(p => p.Name));
        Assert.Equal("void", report.Signature.ReturnType);
        Assert.Contains("suggested signature: void Extract(int bonus)", formatted);

        // The void-ness has an explanation in the report: the composite
        // trailing return is not nameable in v1.
        Assert.Contains(report.Notes, n => n.Contains("composite return expression (score + bonus)", StringComparison.Ordinal));
    }

    // ---------------------------------------------------------------------
    // The report the CLI prints, pinned EXACTLY for one fixture selection
    // (acceptance: "CLI report on the fixture matches the tests"). Heaviest
    // full body is the richest case: raw buckets (params include the
    // declared-inside best/i — the promotion happens only in the signature),
    // extract-first with the invocation flag, no notes, signature last.
    // ---------------------------------------------------------------------
    [Fact]
    public void Formatted_report_for_Heaviest_matches_the_CLI_output_exactly()
    {
        var (_, formatted) = Compose(87, 93);

        var expected =
            "3 statement(s) selected, lines 87..93 in Heaviest(): LocalDeclarationStatement, ForStatement, ReturnStatement\n" +
            "params: best (Widget) [ref]\n" +
            "params: count (int) [in]\n" +
            "params: i (int) [ref]\n" +
            "params: widgets (List<Widget>) [in]\n" +
            "returns: best (Widget)\n" +
            "locals: i\n" +
            "extract-first:\n" +
            "  - widgets[0] — List<Widget>.this[int] ×1\n" +
            "  - best.Bigger(widgets[i]) — Widget.Bigger(Widget) ×1 [hoisting changes eval count]\n" +
            "  - widgets[i] — List<Widget>.this[int] ×1\n" +
            "suggested signature: Widget Extract(int count, List<Widget> widgets)\n";

        Assert.Equal(expected, formatted);
    }

    private static (ExtractionReport Report, string Formatted) Compose(int startLine, int endLine)
    {
        var (tree, compilation) = DemoFixture.Load();
        var model = compilation.GetSemanticModel(tree);

        var resolved = SelectionResolver.Resolve(tree, startLine, endLine);
        Assert.True(resolved.Succeeded, resolved.Error);

        var report = ExtractionReporter.Compose(model, resolved);
        return (report, ReportFormatter.Format(report));
    }
}