feat(implementation-sweep): run one campaign against every implementation of a requirement

installs, builds and serves each implementation on its own port, then hands the campaign tool the same seed slice, step budget and generator for all of them, so a difference between implementations is not a difference in exploration. the generator and platform are fixed rather than exposed.

cmd/internal-tools/implementation-sweep/sweep_test.go

@@ -0,0 +1,114 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestDiscoverImplementations_NameOrderAndOnePortEach(t *testing.T) {
+	directory := t.TempDir()
+	for _, name := range []string{"impl-03", "impl-01", "impl-10", "impl-02", "scaffold", ".DS_Store"} {
+		if err := os.MkdirAll(filepath.Join(directory, name), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := os.WriteFile(filepath.Join(directory, "impl-notes.md"), []byte("not a directory"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	found, err := discoverImplementations(directory, 5300)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []implementation{
+		{Name: "impl-01", Port: 5300},
+		{Name: "impl-02", Port: 5301},
+		{Name: "impl-03", Port: 5302},
+		{Name: "impl-10", Port: 5303},
+	}
+	if len(found) != len(want) {
+		t.Fatalf(
+			"got %d implementations, want %d: %v",
+			len(found),
+			len(want),
+			found,
+		)
+	}
+	for index, target := range found {
+		if target.Name != want[index].Name || target.Port != want[index].Port {
+			t.Errorf(
+				"position %d: got %s on %d, want %s on %d",
+				index,
+				target.Name,
+				target.Port,
+				want[index].Name,
+				want[index].Port,
+			)
+		}
+		if target.Directory != filepath.Join(directory, want[index].Name) {
+			t.Errorf("%s directory: got %q", target.Name, target.Directory)
+		}
+	}
+}
+
+func TestDiscoverImplementations_EmptyDirectoryIsRefused(t *testing.T) {
+	_, err := discoverImplementations(t.TempDir(), 5300)
+	if err == nil || !strings.Contains(err.Error(), "no impl-* directories") {
+		t.Fatalf("got %v, want a refusal naming impl-*", err)
+	}
+}
+
+// A binary that is not there fails once, before anything is installed, rather
+// than twenty-four times after the sweep has spent its build time.
+func TestRunSweep_StopsBeforeItInstallsAnythingWhenABinaryIsMissing(
+	t *testing.T,
+) {
+	implementations := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(implementations, "impl-01"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	output := filepath.Join(t.TempDir(), "campaigns")
+	configuration := config{
+		implementationsDirectory: implementations,
+		outputDirectory:          output,
+		basePort:                 5300,
+		concurrency:              1,
+		bunPath:                  "bun",
+		campaignPath:             "campaign-that-is-not-installed",
+		sanderlingPath:           "sanderling",
+	}
+	err := runSweep(t.Context(), configuration, os.Stdout)
+	if err == nil || !strings.Contains(err.Error(), "--campaign") {
+		t.Fatalf("got %v, want the missing campaign binary named", err)
+	}
+	if _, err := os.Stat(output); !os.IsNotExist(err) {
+		t.Errorf(
+			"the sweep created %s before it checked it could run: %v",
+			output,
+			err,
+		)
+	}
+}
+
+func TestRunSweep_RefusesADirectoryThatAlreadyHoldsASweep(t *testing.T) {
+	implementations := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(implementations, "impl-01"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	output := t.TempDir()
+	if err := os.WriteFile(filepath.Join(output, manifestFileName), []byte("{}"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	configuration := config{
+		implementationsDirectory: implementations,
+		outputDirectory:          output,
+		basePort:                 5300,
+		concurrency:              1,
+	}
+	if err := runSweep(t.Context(), configuration, os.Stdout); err == nil ||
+		!strings.Contains(err.Error(), "already exists") {
+		t.Fatalf("got %v, want a refusal to reuse the directory", err)
+	}
+}