feat: config parsing

go.mod

@@ -1,3 +1,5 @@
 module miro
 
 go 1.25.5
+
+require github.com/BurntSushi/toml v1.5.0

go.sum

@@ -0,0 +1,2 @@
+github.com/BurntSushi/toml v1.5.0 h1:W5quZX/G/csjUnuI8SUYlsHs9M38FC7znL0lIO+DvMg=
+github.com/BurntSushi/toml v1.5.0/go.mod h1:ukJfTF/6rtPPRCnwkur4qwRxa8vTRFBF0uk2lLoLwho=

internal/config/config.go

@@ -0,0 +1,40 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/BurntSushi/toml"
+)
+
+type Config struct {
+	TestDir    string
+	HasTestDir bool
+}
+
+type tomlConfig struct {
+	Miro tomlMiroConfig `toml:"miro"`
+}
+
+type tomlMiroConfig struct {
+	TestDir string `toml:"test_dir"`
+}
+
+// ReadConfig reads miro.toml and reports whether [miro].test_dir was explicitly set.
+func ReadConfig(path string) (Config, error) {
+	var raw tomlConfig
+
+	meta, err := toml.DecodeFile(path, &raw)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return Config{}, err
+		}
+		return Config{}, fmt.Errorf("failed to read %s: %v", path, err)
+	}
+
+	return Config{
+		TestDir:    raw.Miro.TestDir,
+		HasTestDir: meta.IsDefined("miro", "test_dir"),
+	}, nil
+}

internal/config/config_test.go

@@ -0,0 +1,60 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReadConfig(t *testing.T) {
+	tests := []struct {
+		name        string
+		content     string
+		wantDir     string
+		wantHasDir  bool
+		wantReadErr bool
+	}{
+		{
+			name:       "with test dir",
+			content:    "[miro]\ntest_dir = \"custom/suite\"\n",
+			wantDir:    "custom/suite",
+			wantHasDir: true,
+		},
+		{
+			name:       "without test dir",
+			content:    "[miro]\n",
+			wantHasDir: false,
+		},
+		{
+			name:        "invalid toml",
+			content:     "[miro]\ntest_dir = [\n",
+			wantReadErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			path := filepath.Join(t.TempDir(), "miro.toml")
+			if err := os.WriteFile(path, []byte(tt.content), 0o644); err != nil {
+				t.Fatalf("WriteFile() error = %v", err)
+			}
+
+			got, err := ReadConfig(path)
+			if tt.wantReadErr {
+				if err == nil {
+					t.Fatal("ReadConfig() error = nil, want error")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("ReadConfig() error = %v", err)
+			}
+			if got.TestDir != tt.wantDir {
+				t.Fatalf("ReadConfig() TestDir = %q, want %q", got.TestDir, tt.wantDir)
+			}
+			if got.HasTestDir != tt.wantHasDir {
+				t.Fatalf("ReadConfig() HasTestDir = %v, want %v", got.HasTestDir, tt.wantHasDir)
+			}
+		})
+	}
+}