vendor/github.com/sdboyer/gps/solve_test.go - third_party/Masterminds/glide - Git at Google

 package gps

 import (
 	"bytes"
 	"flag"
 	"fmt"
 	"io/ioutil"
 	"log"
 	"math/rand"
 	"os"
 	"reflect"
 	"sort"
 	"strconv"
 	"strings"
 	"testing"
 )

 var fixtorun string

 // TODO(sdboyer) regression test ensuring that locks with only revs for projects don't cause errors
 func init() {
 	flag.StringVar(&fixtorun, "gps.fix", "", "A single fixture to run in TestBasicSolves or TestBimodalSolves")
 	overrideMkBridge()
 }

 // sets the mkBridge global func to one that allows virtualized RootDirs
 func overrideMkBridge() {
 	// For all tests, override the base bridge with the depspecBridge that skips
 	// verifyRootDir calls
 	mkBridge = func(s *solver, sm SourceManager) sourceBridge {
 		return &depspecBridge{
 			&bridge{
 				sm:     sm,
 				s:      s,
 				vlists: make(map[ProjectIdentifier][]Version),
 			},
 		}
 	}
 }

 var stderrlog = log.New(os.Stderr, "", 0)

 func fixSolve(params SolveParameters, sm SourceManager) (Solution, error) {
 	if testing.Verbose() {
 		params.Trace = true
 		params.TraceLogger = stderrlog
 	}

 	s, err := Prepare(params, sm)
 	if err != nil {
 		return nil, err
 	}

 	return s.Solve()
 }

 // Test all the basic table fixtures.
 //
 // Or, just the one named in the fix arg.
 func TestBasicSolves(t *testing.T) {
 	if fixtorun != "" {
 		if fix, exists := basicFixtures[fixtorun]; exists {
 			solveBasicsAndCheck(fix, t)
 		}
 	} else {
 		// sort them by their keys so we get stable output
 		var names []string
 		for n := range basicFixtures {
 			names = append(names, n)
 		}

 		sort.Strings(names)
 		for _, n := range names {
 			solveBasicsAndCheck(basicFixtures[n], t)
 			if testing.Verbose() {
 				// insert a line break between tests
 				stderrlog.Println("")
 			}
 		}
 	}
 }

 func solveBasicsAndCheck(fix basicFixture, t *testing.T) (res Solution, err error) {
 	if testing.Verbose() {
 		stderrlog.Printf("[[fixture %q]]", fix.n)
 	}
 	sm := newdepspecSM(fix.ds, nil)

 	params := SolveParameters{
 		RootDir:         string(fix.ds[0].n),
 		RootPackageTree: fix.rootTree(),
 		Manifest:        fix.rootmanifest(),
 		Lock:            dummyLock{},
 		Downgrade:       fix.downgrade,
 		ChangeAll:       fix.changeall,
 	}

 	if fix.l != nil {
 		params.Lock = fix.l
 	}

 	res, err = fixSolve(params, sm)

 	return fixtureSolveSimpleChecks(fix, res, err, t)
 }

 // Test all the bimodal table fixtures.
 //
 // Or, just the one named in the fix arg.
 func TestBimodalSolves(t *testing.T) {
 	if fixtorun != "" {
 		if fix, exists := bimodalFixtures[fixtorun]; exists {
 			solveBimodalAndCheck(fix, t)
 		}
 	} else {
 		// sort them by their keys so we get stable output
 		var names []string
 		for n := range bimodalFixtures {
 			names = append(names, n)
 		}

 		sort.Strings(names)
 		for _, n := range names {
 			solveBimodalAndCheck(bimodalFixtures[n], t)
 			if testing.Verbose() {
 				// insert a line break between tests
 				stderrlog.Println("")
 			}
 		}
 	}
 }

 func solveBimodalAndCheck(fix bimodalFixture, t *testing.T) (res Solution, err error) {
 	if testing.Verbose() {
 		stderrlog.Printf("[[fixture %q]]", fix.n)
 	}
 	sm := newbmSM(fix)

 	params := SolveParameters{
 		RootDir:         string(fix.ds[0].n),
 		RootPackageTree: fix.rootTree(),
 		Manifest:        fix.rootmanifest(),
 		Lock:            dummyLock{},
 		Downgrade:       fix.downgrade,
 		ChangeAll:       fix.changeall,
 	}

 	if fix.l != nil {
 		params.Lock = fix.l
 	}

 	res, err = fixSolve(params, sm)

 	return fixtureSolveSimpleChecks(fix, res, err, t)
 }

 func fixtureSolveSimpleChecks(fix specfix, soln Solution, err error, t *testing.T) (Solution, error) {
 	ppi := func(id ProjectIdentifier) string {
 		// need this so we can clearly tell if there's a NetworkName or not
 		if id.NetworkName == "" {
 			return string(id.ProjectRoot)
 		}
 		return fmt.Sprintf("%s (from %s)", id.ProjectRoot, id.NetworkName)
 	}

 	pv := func(v Version) string {
 		if pv, ok := v.(PairedVersion); ok {
 			return fmt.Sprintf("%s (%s)", pv.Unpair(), pv.Underlying())
 		}
 		return v.String()
 	}

 	fixfail := fix.failure()
 	if err != nil {
 		if fixfail == nil {
 			t.Errorf("(fixture: %q) Solve failed unexpectedly:\n%s", fix.name(), err)
 		} else if !reflect.DeepEqual(fixfail, err) {
 			// TODO(sdboyer) reflect.DeepEqual works for now, but once we start
 			// modeling more complex cases, this should probably become more robust
 			t.Errorf("(fixture: %q) Failure mismatch:\n\t(GOT): %s\n\t(WNT): %s", fix.name(), err, fixfail)
 		}
 	} else if fixfail != nil {
 		var buf bytes.Buffer
 		fmt.Fprintf(&buf, "(fixture: %q) Solver succeeded, but expecting failure:\n%s\nProjects in solution:", fix.name(), fixfail)
 		for _, p := range soln.Projects() {
 			fmt.Fprintf(&buf, "\n\t- %s at %s", ppi(p.Ident()), p.Version())
 		}
 		t.Error(buf.String())
 	} else {
 		r := soln.(solution)
 		if fix.maxTries() > 0 && r.Attempts() > fix.maxTries() {
 			t.Errorf("(fixture: %q) Solver completed in %v attempts, but expected %v or fewer", fix.name(), r.att, fix.maxTries())
 		}

 		// Dump result projects into a map for easier interrogation
 		rp := make(map[ProjectIdentifier]Version)
 		for _, p := range r.p {
 			pa := p.toAtom()
 			rp[pa.id] = pa.v
 		}

 		fixlen, rlen := len(fix.solution()), len(rp)
 		if fixlen != rlen {
 			// Different length, so they definitely disagree
 			t.Errorf("(fixture: %q) Solver reported %v package results, result expected %v", fix.name(), rlen, fixlen)
 		}

 		// Whether or not len is same, still have to verify that results agree
 		// Walk through fixture/expected results first
 		for p, v := range fix.solution() {
 			if av, exists := rp[p]; !exists {
 				t.Errorf("(fixture: %q) Project %q expected but missing from results", fix.name(), ppi(p))
 			} else {
 				// delete result from map so we skip it on the reverse pass
 				delete(rp, p)
 				if v != av {
 					t.Errorf("(fixture: %q) Expected version %q of project %q, but actual version was %q", fix.name(), pv(v), ppi(p), pv(av))
 				}
 			}
 		}

 		// Now walk through remaining actual results
 		for p, v := range rp {
 			if fv, exists := fix.solution()[p]; !exists {
 				t.Errorf("(fixture: %q) Unexpected project %q present in results", fix.name(), ppi(p))
 			} else if v != fv {
 				t.Errorf("(fixture: %q) Got version %q of project %q, but expected version was %q", fix.name(), pv(v), ppi(p), pv(fv))
 			}
 		}
 	}

 	return soln, err
 }

 // This tests that, when a root lock is underspecified (has only a version) we
 // don't allow a match on that version from a rev in the manifest. We may allow
 // this in the future, but disallow it for now because going from an immutable
 // requirement to a mutable lock automagically is a bad direction that could
 // produce weird side effects.
 func TestRootLockNoVersionPairMatching(t *testing.T) {
 	fix := basicFixture{
 		n: "does not match unpaired lock versions with paired real versions",
 		ds: []depspec{
 			mkDepspec("root 0.0.0", "foo *"), // foo's constraint rewritten below to foorev
 			mkDepspec("foo 1.0.0", "bar 1.0.0"),
 			mkDepspec("foo 1.0.1 foorev", "bar 1.0.1"),
 			mkDepspec("foo 1.0.2 foorev", "bar 1.0.2"),
 			mkDepspec("bar 1.0.0"),
 			mkDepspec("bar 1.0.1"),
 			mkDepspec("bar 1.0.2"),
 		},
 		l: mklock(
 			"foo 1.0.1",
 		),
 		r: mksolution(
 			"foo 1.0.2 foorev",
 			"bar 1.0.2",
 		),
 	}

 	pd := fix.ds[0].deps[0]
 	pd.Constraint = Revision("foorev")
 	fix.ds[0].deps[0] = pd

 	sm := newdepspecSM(fix.ds, nil)

 	l2 := make(fixLock, 1)
 	copy(l2, fix.l)
 	l2[0].v = nil

 	params := SolveParameters{
 		RootDir:         string(fix.ds[0].n),
 		RootPackageTree: fix.rootTree(),
 		Manifest:        fix.rootmanifest(),
 		Lock:            l2,
 	}

 	res, err := fixSolve(params, sm)

 	fixtureSolveSimpleChecks(fix, res, err, t)
 }

 func TestBadSolveOpts(t *testing.T) {
 	pn := strconv.FormatInt(rand.Int63(), 36)
 	fix := basicFixtures["no dependencies"]
 	fix.ds[0].n = ProjectRoot(pn)

 	sm := newdepspecSM(fix.ds, nil)
 	params := SolveParameters{}

 	_, err := Prepare(params, nil)
 	if err == nil {
 		t.Errorf("Prepare should have errored on nil SourceManager")
 	} else if !strings.Contains(err.Error(), "non-nil SourceManager") {
 		t.Error("Prepare should have given error on nil SourceManager, but gave:", err)
 	}

 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Prepare should have errored on empty root")
 	} else if !strings.Contains(err.Error(), "non-empty root directory") {
 		t.Error("Prepare should have given error on empty root, but gave:", err)
 	}

 	params.RootDir = pn
 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Prepare should have errored on empty name")
 	} else if !strings.Contains(err.Error(), "non-empty import root") {
 		t.Error("Prepare should have given error on empty import root, but gave:", err)
 	}

 	params.RootPackageTree = PackageTree{
 		ImportRoot: pn,
 	}
 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Prepare should have errored on empty name")
 	} else if !strings.Contains(err.Error(), "at least one package") {
 		t.Error("Prepare should have given error on empty import root, but gave:", err)
 	}

 	params.RootPackageTree = PackageTree{
 		ImportRoot: pn,
 		Packages: map[string]PackageOrErr{
 			pn: {
 				P: Package{
 					ImportPath: pn,
 					Name:       pn,
 				},
 			},
 		},
 	}
 	params.Trace = true
 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Should have errored on trace with no logger")
 	} else if !strings.Contains(err.Error(), "no logger provided") {
 		t.Error("Prepare should have given error on missing trace logger, but gave:", err)
 	}
 	params.TraceLogger = log.New(ioutil.Discard, "", 0)

 	params.Manifest = simpleRootManifest{
 		ovr: ProjectConstraints{
 			ProjectRoot("foo"): ProjectProperties{},
 		},
 	}
 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Should have errored on override with empty ProjectProperties")
 	} else if !strings.Contains(err.Error(), "foo, but without any non-zero properties") {
 		t.Error("Prepare should have given error override with empty ProjectProperties, but gave:", err)
 	}
 	params.Manifest = nil

 	_, err = Prepare(params, sm)
 	if err != nil {
 		t.Error("Basic conditions satisfied, prepare should have completed successfully, err as:", err)
 	}

 	// swap out the test mkBridge override temporarily, just to make sure we get
 	// the right error
 	mkBridge = func(s *solver, sm SourceManager) sourceBridge {
 		return &bridge{
 			sm:     sm,
 			s:      s,
 			vlists: make(map[ProjectIdentifier][]Version),
 		}
 	}

 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Should have errored on nonexistent root")
 	} else if !strings.Contains(err.Error(), "could not read project root") {
 		t.Error("Prepare should have given error nonexistent project root dir, but gave:", err)
 	}

 	// Pointing it at a file should also be an err
 	params.RootDir = "solve_test.go"
 	_, err = Prepare(params, sm)
 	if err == nil {
 		t.Errorf("Should have errored on file for RootDir")
 	} else if !strings.Contains(err.Error(), "is a file, not a directory") {
 		t.Error("Prepare should have given error on file as RootDir, but gave:", err)
 	}

 	// swap them back...not sure if this matters, but just in case
 	overrideMkBridge()
 }
	package gps

	import (
	"bytes"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"math/rand"
	"os"
	"reflect"
	"sort"
	"strconv"
	"strings"
	"testing"
	)

	var fixtorun string

	// TODO(sdboyer) regression test ensuring that locks with only revs for projects don't cause errors
	func init() {
	flag.StringVar(&fixtorun, "gps.fix", "", "A single fixture to run in TestBasicSolves or TestBimodalSolves")
	overrideMkBridge()
	}

	// sets the mkBridge global func to one that allows virtualized RootDirs
	func overrideMkBridge() {
	// For all tests, override the base bridge with the depspecBridge that skips
	// verifyRootDir calls
	mkBridge = func(s *solver, sm SourceManager) sourceBridge {
	return &depspecBridge{
	&bridge{
	sm: sm,
	s: s,
	vlists: make(map[ProjectIdentifier][]Version),
	},
	}
	}
	}

	var stderrlog = log.New(os.Stderr, "", 0)

	func fixSolve(params SolveParameters, sm SourceManager) (Solution, error) {
	if testing.Verbose() {
	params.Trace = true
	params.TraceLogger = stderrlog
	}

	s, err := Prepare(params, sm)
	if err != nil {
	return nil, err
	}

	return s.Solve()
	}

	// Test all the basic table fixtures.
	//
	// Or, just the one named in the fix arg.
	func TestBasicSolves(t *testing.T) {
	if fixtorun != "" {
	if fix, exists := basicFixtures[fixtorun]; exists {
	solveBasicsAndCheck(fix, t)
	}
	} else {
	// sort them by their keys so we get stable output
	var names []string
	for n := range basicFixtures {
	names = append(names, n)
	}

	sort.Strings(names)
	for _, n := range names {
	solveBasicsAndCheck(basicFixtures[n], t)
	if testing.Verbose() {
	// insert a line break between tests
	stderrlog.Println("")
	}
	}
	}
	}

	func solveBasicsAndCheck(fix basicFixture, t *testing.T) (res Solution, err error) {
	if testing.Verbose() {
	stderrlog.Printf("[[fixture %q]]", fix.n)
	}
	sm := newdepspecSM(fix.ds, nil)

	params := SolveParameters{
	RootDir: string(fix.ds[0].n),
	RootPackageTree: fix.rootTree(),
	Manifest: fix.rootmanifest(),
	Lock: dummyLock{},
	Downgrade: fix.downgrade,
	ChangeAll: fix.changeall,
	}

	if fix.l != nil {
	params.Lock = fix.l
	}

	res, err = fixSolve(params, sm)

	return fixtureSolveSimpleChecks(fix, res, err, t)
	}

	// Test all the bimodal table fixtures.
	//
	// Or, just the one named in the fix arg.
	func TestBimodalSolves(t *testing.T) {
	if fixtorun != "" {
	if fix, exists := bimodalFixtures[fixtorun]; exists {
	solveBimodalAndCheck(fix, t)
	}
	} else {
	// sort them by their keys so we get stable output
	var names []string
	for n := range bimodalFixtures {
	names = append(names, n)
	}

	sort.Strings(names)
	for _, n := range names {
	solveBimodalAndCheck(bimodalFixtures[n], t)
	if testing.Verbose() {
	// insert a line break between tests
	stderrlog.Println("")
	}
	}
	}
	}

	func solveBimodalAndCheck(fix bimodalFixture, t *testing.T) (res Solution, err error) {
	if testing.Verbose() {
	stderrlog.Printf("[[fixture %q]]", fix.n)
	}
	sm := newbmSM(fix)

	params := SolveParameters{
	RootDir: string(fix.ds[0].n),
	RootPackageTree: fix.rootTree(),
	Manifest: fix.rootmanifest(),
	Lock: dummyLock{},
	Downgrade: fix.downgrade,
	ChangeAll: fix.changeall,
	}

	if fix.l != nil {
	params.Lock = fix.l
	}

	res, err = fixSolve(params, sm)

	return fixtureSolveSimpleChecks(fix, res, err, t)
	}

	func fixtureSolveSimpleChecks(fix specfix, soln Solution, err error, t *testing.T) (Solution, error) {
	ppi := func(id ProjectIdentifier) string {
	// need this so we can clearly tell if there's a NetworkName or not
	if id.NetworkName == "" {
	return string(id.ProjectRoot)
	}
	return fmt.Sprintf("%s (from %s)", id.ProjectRoot, id.NetworkName)
	}

	pv := func(v Version) string {
	if pv, ok := v.(PairedVersion); ok {
	return fmt.Sprintf("%s (%s)", pv.Unpair(), pv.Underlying())
	}
	return v.String()
	}

	fixfail := fix.failure()
	if err != nil {
	if fixfail == nil {
	t.Errorf("(fixture: %q) Solve failed unexpectedly:\n%s", fix.name(), err)
	} else if !reflect.DeepEqual(fixfail, err) {
	// TODO(sdboyer) reflect.DeepEqual works for now, but once we start
	// modeling more complex cases, this should probably become more robust
	t.Errorf("(fixture: %q) Failure mismatch:\n\t(GOT): %s\n\t(WNT): %s", fix.name(), err, fixfail)
	}
	} else if fixfail != nil {
	var buf bytes.Buffer
	fmt.Fprintf(&buf, "(fixture: %q) Solver succeeded, but expecting failure:\n%s\nProjects in solution:", fix.name(), fixfail)
	for _, p := range soln.Projects() {
	fmt.Fprintf(&buf, "\n\t- %s at %s", ppi(p.Ident()), p.Version())
	}
	t.Error(buf.String())
	} else {
	r := soln.(solution)
	if fix.maxTries() > 0 && r.Attempts() > fix.maxTries() {
	t.Errorf("(fixture: %q) Solver completed in %v attempts, but expected %v or fewer", fix.name(), r.att, fix.maxTries())
	}

	// Dump result projects into a map for easier interrogation
	rp := make(map[ProjectIdentifier]Version)
	for _, p := range r.p {
	pa := p.toAtom()
	rp[pa.id] = pa.v
	}

	fixlen, rlen := len(fix.solution()), len(rp)
	if fixlen != rlen {
	// Different length, so they definitely disagree
	t.Errorf("(fixture: %q) Solver reported %v package results, result expected %v", fix.name(), rlen, fixlen)
	}

	// Whether or not len is same, still have to verify that results agree
	// Walk through fixture/expected results first
	for p, v := range fix.solution() {
	if av, exists := rp[p]; !exists {
	t.Errorf("(fixture: %q) Project %q expected but missing from results", fix.name(), ppi(p))
	} else {
	// delete result from map so we skip it on the reverse pass
	delete(rp, p)
	if v != av {
	t.Errorf("(fixture: %q) Expected version %q of project %q, but actual version was %q", fix.name(), pv(v), ppi(p), pv(av))
	}
	}
	}

	// Now walk through remaining actual results
	for p, v := range rp {
	if fv, exists := fix.solution()[p]; !exists {
	t.Errorf("(fixture: %q) Unexpected project %q present in results", fix.name(), ppi(p))
	} else if v != fv {
	t.Errorf("(fixture: %q) Got version %q of project %q, but expected version was %q", fix.name(), pv(v), ppi(p), pv(fv))
	}
	}
	}

	return soln, err
	}

	// This tests that, when a root lock is underspecified (has only a version) we
	// don't allow a match on that version from a rev in the manifest. We may allow
	// this in the future, but disallow it for now because going from an immutable
	// requirement to a mutable lock automagically is a bad direction that could
	// produce weird side effects.
	func TestRootLockNoVersionPairMatching(t *testing.T) {
	fix := basicFixture{
	n: "does not match unpaired lock versions with paired real versions",
	ds: []depspec{
	mkDepspec("root 0.0.0", "foo *"), // foo's constraint rewritten below to foorev
	mkDepspec("foo 1.0.0", "bar 1.0.0"),
	mkDepspec("foo 1.0.1 foorev", "bar 1.0.1"),
	mkDepspec("foo 1.0.2 foorev", "bar 1.0.2"),
	mkDepspec("bar 1.0.0"),
	mkDepspec("bar 1.0.1"),
	mkDepspec("bar 1.0.2"),
	},
	l: mklock(
	"foo 1.0.1",
	),
	r: mksolution(
	"foo 1.0.2 foorev",
	"bar 1.0.2",
	),
	}

	pd := fix.ds[0].deps[0]
	pd.Constraint = Revision("foorev")
	fix.ds[0].deps[0] = pd

	sm := newdepspecSM(fix.ds, nil)

	l2 := make(fixLock, 1)
	copy(l2, fix.l)
	l2[0].v = nil

	params := SolveParameters{
	RootDir: string(fix.ds[0].n),
	RootPackageTree: fix.rootTree(),
	Manifest: fix.rootmanifest(),
	Lock: l2,
	}

	res, err := fixSolve(params, sm)

	fixtureSolveSimpleChecks(fix, res, err, t)
	}

	func TestBadSolveOpts(t *testing.T) {
	pn := strconv.FormatInt(rand.Int63(), 36)
	fix := basicFixtures["no dependencies"]
	fix.ds[0].n = ProjectRoot(pn)

	sm := newdepspecSM(fix.ds, nil)
	params := SolveParameters{}

	_, err := Prepare(params, nil)
	if err == nil {
	t.Errorf("Prepare should have errored on nil SourceManager")
	} else if !strings.Contains(err.Error(), "non-nil SourceManager") {
	t.Error("Prepare should have given error on nil SourceManager, but gave:", err)
	}

	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Prepare should have errored on empty root")
	} else if !strings.Contains(err.Error(), "non-empty root directory") {
	t.Error("Prepare should have given error on empty root, but gave:", err)
	}

	params.RootDir = pn
	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Prepare should have errored on empty name")
	} else if !strings.Contains(err.Error(), "non-empty import root") {
	t.Error("Prepare should have given error on empty import root, but gave:", err)
	}

	params.RootPackageTree = PackageTree{
	ImportRoot: pn,
	}
	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Prepare should have errored on empty name")
	} else if !strings.Contains(err.Error(), "at least one package") {
	t.Error("Prepare should have given error on empty import root, but gave:", err)
	}

	params.RootPackageTree = PackageTree{
	ImportRoot: pn,
	Packages: map[string]PackageOrErr{
	pn: {
	P: Package{
	ImportPath: pn,
	Name: pn,
	},
	},
	},
	}
	params.Trace = true
	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Should have errored on trace with no logger")
	} else if !strings.Contains(err.Error(), "no logger provided") {
	t.Error("Prepare should have given error on missing trace logger, but gave:", err)
	}
	params.TraceLogger = log.New(ioutil.Discard, "", 0)

	params.Manifest = simpleRootManifest{
	ovr: ProjectConstraints{
	ProjectRoot("foo"): ProjectProperties{},
	},
	}
	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Should have errored on override with empty ProjectProperties")
	} else if !strings.Contains(err.Error(), "foo, but without any non-zero properties") {
	t.Error("Prepare should have given error override with empty ProjectProperties, but gave:", err)
	}
	params.Manifest = nil

	_, err = Prepare(params, sm)
	if err != nil {
	t.Error("Basic conditions satisfied, prepare should have completed successfully, err as:", err)
	}

	// swap out the test mkBridge override temporarily, just to make sure we get
	// the right error
	mkBridge = func(s *solver, sm SourceManager) sourceBridge {
	return &bridge{
	sm: sm,
	s: s,
	vlists: make(map[ProjectIdentifier][]Version),
	}
	}

	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Should have errored on nonexistent root")
	} else if !strings.Contains(err.Error(), "could not read project root") {
	t.Error("Prepare should have given error nonexistent project root dir, but gave:", err)
	}

	// Pointing it at a file should also be an err
	params.RootDir = "solve_test.go"
	_, err = Prepare(params, sm)
	if err == nil {
	t.Errorf("Should have errored on file for RootDir")
	} else if !strings.Contains(err.Error(), "is a file, not a directory") {
	t.Error("Prepare should have given error on file as RootDir, but gave:", err)
	}

	// swap them back...not sure if this matters, but just in case
	overrideMkBridge()
	}