diff --git a/packages/libprecious/test/index.js b/packages/libprecious/test/index.js
index 162df31..0096aa5 100644
--- a/packages/libprecious/test/index.js
+++ b/packages/libprecious/test/index.js
@@ -85,3 +85,424 @@ test('it works', t => {
         })
     })
 })
+
+test('it archives devdeps by default', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          devDependencies: {
+            bar: '^1.0.0'
+          }
+        }),
+        'package-lock.json': File({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity,
+              dev: true
+            }
+          }
+        })
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY})
+      tnock(t, REGISTRY).get('/bar/-/bar-1.0.1.tgz').reply(200, tgzData)
+      const archivedResolved = `file:archived-packages/bar-1.0.1-${ssri.parse(integrity).hexDigest().slice(0, 9)}.tar`
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => fs.readFileAsync('package-lock.json', 'utf8'))
+        .then(JSON.parse)
+        .then(pkgLock => {
+          t.equal(
+            pkgLock.dependencies.bar.resolved,
+            archivedResolved,
+            'resolved field updated in package-lock'
+          )
+          return fs.readFileAsync(archivedResolved.substr(5))
+            .then(tarData => {
+              const newSri = pkgLock.dependencies.bar.integrity
+              t.ok(tarData.length > tgzData.length, 'tarball is gunzipped')
+              t.ok(
+                ssri.checkData(tarData, newSri),
+                'archived tarball passes integrity check'
+              )
+              t.ok(
+                ssri.checkData(tgzData, newSri),
+                'updated integrity field still matches old tgzData'
+              )
+              t.notOk(
+                ssri.checkData('blah', newSri),
+                'updated integrity field is actually checking data at all'
+              )
+            })
+        })
+    })
+})
+
+test('it does not archive devdeps with `only=production` config', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          devDependencies: {
+            bar: '^1.0.0'
+          }
+        }),
+        'package-lock.json': File({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity,
+              dev: true
+            }
+          }
+        })
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY, only: 'production'})
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => fs.readFileAsync('package-lock.json', 'utf8'))
+        .then(JSON.parse)
+        .then(pkgLock => {
+          t.equal(
+            pkgLock.dependencies.bar.resolved,
+            REGISTRY + 'bar/-/bar-1.0.1.tgz',
+            'resolved field not updated in package-lock'
+          )
+        })
+    })
+})
+
+test('it works with npm-shrinkwrap files', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          dependencies: {
+            bar: '^1.0.0'
+          }
+        }),
+        'npm-shrinkwrap.json': File({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity
+            }
+          }
+        })
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY})
+      tnock(t, REGISTRY).get('/bar/-/bar-1.0.1.tgz').reply(200, tgzData)
+      const archivedResolved = `file:archived-packages/bar-1.0.1-${ssri.parse(integrity).hexDigest().slice(0, 9)}.tar`
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => fs.readFileAsync('npm-shrinkwrap.json', 'utf8'))
+        .then(JSON.parse)
+        .then(pkgLock => {
+          t.equal(
+            pkgLock.dependencies.bar.resolved,
+            archivedResolved,
+            'resolved field updated in npm-shrinkwrap'
+          )
+          return fs.readFileAsync(archivedResolved.substr(5))
+            .then(tarData => {
+              const newSri = pkgLock.dependencies.bar.integrity
+              t.ok(tarData.length > tgzData.length, 'tarball is gunzipped')
+              t.ok(
+                ssri.checkData(tarData, newSri),
+                'archived tarball passes integrity check'
+              )
+              t.ok(
+                ssri.checkData(tgzData, newSri),
+                'updated integrity field still matches old tgzData'
+              )
+              t.notOk(
+                ssri.checkData('blah', newSri),
+                'updated integrity field is actually checking data at all'
+              )
+            })
+        })
+    })
+})
+
+test('fails if package-lock.json is out of sync with package.json', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          dependencies: {
+            bar: '^1.0.0',
+            baz: '^2.0.0'
+          }
+        }),
+        'package-lock.json': File({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity
+            }
+          }
+        })
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY, loglevel: 'warn'})
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => { throw new Error('Should not pass') }, error => {
+          t.type(
+            error, Error,
+            'given an Error object'
+          )
+          t.match(
+            error.message, /are in sync/i,
+            'error message reflects lack of package-lock.json'
+          )
+          t.match(
+            error.message, /Missing: baz@\^2.0.0/i,
+            'error message includes summary of missing deps'
+          )
+        })
+    })
+})
+
+test('fails if package-lock.json and npm-shrinkwrap are both missing', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          dependencies: {
+            bar: '^1.0.0'
+          }
+        })
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY})
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => { throw new Error('Should not pass') }, error => {
+          t.type(
+            error, Error,
+            'given an Error object'
+          )
+          t.match(
+            error.message, /we can only install packages with an existing package-lock.json/i,
+            'error message reflects lack of package-lock.json'
+          )
+        })
+    })
+})
+
+test('fails if package.json is malformed', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File(JSON.stringify({
+          name: 'foo',
+          version: '1.2.3',
+          dependencies: {
+            bar: '^1.0.0'
+          }
+        }) + 'malformed-package!'),
+        'package-lock.json': File({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity
+            }
+          }
+        })
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY})
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => { throw new Error('Should not pass') }, error => {
+          t.type(
+            error, SyntaxError,
+            'given a syntax error object'
+          )
+          t.match(
+            error.message, /unexpected token/i,
+            'error message reflects json parse error'
+          )
+        })
+    })
+})
+
+test('fails if package-lock.json is malformed', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          dependencies: {
+            bar: '^1.0.0'
+          }
+        }),
+        'package-lock.json': File(JSON.stringify({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity
+            }
+          }
+        }) + 'malformed-package!')
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY})
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => { throw new Error('Should not pass') }, error => {
+          t.type(
+            error, SyntaxError,
+            'given a syntax error object'
+          )
+          t.match(
+            error.message, /unexpected token/i,
+            'error message reflects json parse error'
+          )
+        })
+    })
+})
+
+test('fails if npm-shrinkwrap.json is malformed', t => {
+  return mockTar({
+    // This makes the tarball for `bar` itself, to be hosted by tnock
+    'package.json': JSON.stringify({
+      name: 'bar',
+      version: '1.0.1'
+    }),
+    'index.js': 'hi'
+  }, {gzip: true})
+    .then(tgzData => {
+      const integrity = ssri.fromData(tgzData).toString()
+      const fixture = new Tacks(Dir({
+        'package.json': File({
+          name: 'foo',
+          version: '1.2.3',
+          dependencies: {
+            bar: '^1.0.0'
+          }
+        }),
+        'npm-shrinkwrap.json': File(JSON.stringify({
+          name: 'foo',
+          lockfileVersion: 1,
+          requires: true,
+          dependencies: {
+            bar: {
+              version: '1.0.1',
+              resolved: REGISTRY + 'bar/-/bar-1.0.1.tgz',
+              integrity
+            }
+          }
+        }) + 'malformed-package!')
+      }))
+      fixture.create(testDir)
+      const config = mockConfig(testDir, {registry: REGISTRY})
+      return new MyPrecious({log: npmlog, config})
+        .run()
+        .then(() => { throw new Error('Should not pass') }, error => {
+          t.type(
+            error, SyntaxError,
+            'given a syntax error object'
+          )
+          t.match(
+            error.message, /unexpected token/i,
+            'error message reflects json parse error'
+          )
+        })
+    })
+})