refactor: move tunnel pkg down one level (#358)

* refactor: move tunnel pkg down one level

While there, reduce unnecessary dependency on external packages.

* file I forgot to commit

internal/tunnel/psiphon_test.go

@@ -0,0 +1,99 @@
+package tunnel
+
+import (
+	"context"
+	"errors"
+	"os"
+	"testing"
+
+	"github.com/ooni/psiphon/oopsi/github.com/Psiphon-Labs/psiphon-tunnel-core/ClientLibrary/clientlib"
+)
+
+func TestPsiphonWithCancelledContext(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // immediately fail
+	sess := &MockableSession{}
+	tunnel, err := psiphonStart(ctx, &Config{
+		Session:   sess,
+		TunnelDir: "testdata",
+	})
+	if !errors.Is(err, context.Canceled) {
+		t.Fatal("not the error we expected")
+	}
+	if tunnel != nil {
+		t.Fatal("expected nil tunnel here")
+	}
+}
+
+func TestPsiphonWithEmptyTunnelDir(t *testing.T) {
+	ctx := context.Background()
+	sess := &MockableSession{}
+	tunnel, err := psiphonStart(ctx, &Config{
+		Session:   sess,
+		TunnelDir: "",
+	})
+	if !errors.Is(err, ErrEmptyTunnelDir) {
+		t.Fatal("not the error we expected")
+	}
+	if tunnel != nil {
+		t.Fatal("expected nil tunnel here")
+	}
+}
+
+func TestPsiphonFetchPsiphonConfigFailure(t *testing.T) {
+	expected := errors.New("mocked error")
+	sess := &MockableSession{
+		Err: expected,
+	}
+	tunnel, err := psiphonStart(context.Background(), &Config{
+		Session:   sess,
+		TunnelDir: "testdata",
+	})
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if tunnel != nil {
+		t.Fatal("expected nil tunnel here")
+	}
+}
+
+func TestPsiphonMkdirAllFailure(t *testing.T) {
+	expected := errors.New("mocked error")
+	sess := &MockableSession{
+		Result: []byte(`{}`),
+	}
+	tunnel, err := psiphonStart(context.Background(), &Config{
+		Session:   sess,
+		TunnelDir: "testdata",
+		testMkdirAll: func(path string, perm os.FileMode) error {
+			return expected
+		},
+	})
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if tunnel != nil {
+		t.Fatal("expected nil tunnel here")
+	}
+}
+
+func TestPsiphonStartFailure(t *testing.T) {
+	expected := errors.New("mocked error")
+	sess := &MockableSession{
+		Result: []byte(`{}`),
+	}
+	tunnel, err := psiphonStart(context.Background(), &Config{
+		Session:   sess,
+		TunnelDir: "testdata",
+		testStartPsiphon: func(ctx context.Context, config []byte,
+			workdir string) (*clientlib.PsiphonTunnel, error) {
+			return nil, expected
+		},
+	})
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if tunnel != nil {
+		t.Fatal("expected nil tunnel here")
+	}
+}