diff --git a/ci/packages.Tests.ps1 b/ci/packages.Tests.ps1
index 77ecd47..2a2887d 100644
--- a/ci/packages.Tests.ps1
+++ b/ci/packages.Tests.ps1
@@ -285,6 +285,11 @@ Describe 'the real packages.json' {
         $ipi.Count | Should -Be 5
         $ipi.FirstVersion | Select-Object -Unique | Should -Be '4.5.0'
     }
+
+    It 'has every tox.ini install the packages its package depends on' {
+        Get-ToxGaps (Split-Path $PSScriptRoot) $script:Real |
+            Should -BeNullOrEmpty
+    }
 }
 
 }
diff --git a/ci/packages.ps1 b/ci/packages.ps1
index 5043d0a..70e6af0 100644
--- a/ci/packages.ps1
+++ b/ci/packages.ps1
@@ -30,6 +30,51 @@ function Test-PathUnder([string]$Path, [string]$Folder) {
     return $Path -eq $Folder -or $Path.StartsWith("$Folder/")
 }
 
+# Each tox.ini that does not install every package its package depends on,
+# directly or through another, from this checkout, as a line naming what is
+# missing. Taken from a package index instead, a dependency is tested at its
+# last release rather than with the code it is released with.
+function Get-ToxGaps([string]$RepoPath, $Packages = $null) {
+    if ($null -eq $Packages) {
+        $Packages = Get-Packages $RepoPath
+    }
+    $byName = @{}
+    foreach ($package in $Packages) {
+        $byName[$package.Name] = $package
+    }
+    $gaps = @()
+    foreach ($package in $Packages) {
+        $tox = Join-Path $RepoPath $package.Path 'tox.ini'
+        if ((Test-Path $tox) -eq $false) {
+            continue
+        }
+        $text = Get-Content -Raw $tox
+        $needed = [Collections.Generic.HashSet[string]]::new()
+        $queue = [Collections.Generic.Queue[string]]::new()
+        foreach ($name in $package.DependsOn) {
+            $queue.Enqueue($name)
+        }
+        while ($queue.Count -gt 0) {
+            $name = $queue.Dequeue()
+            if ($needed.Add($name) -eq $true) {
+                foreach ($next in $byName[$name].DependsOn) {
+                    $queue.Enqueue($next)
+                }
+            }
+        }
+        foreach ($name in $needed) {
+            $relative = [IO.Path]::GetRelativePath(
+                (Join-Path $RepoPath $package.Path),
+                (Join-Path $RepoPath $byName[$name].Path)).Replace('\', '/')
+            $pattern = '(?m)^\s*-e\s*' + [regex]::Escape($relative) + '/?\s*$'
+            if ($text -notmatch $pattern) {
+                $gaps += "$($package.Path)/tox.ini does not install $name from $relative"
+            }
+        }
+    }
+    return $gaps
+}
+
 # The names of the given packages and of every package that depends on one of
 # them, directly or through another.
 function Get-DependentClosure($Packages, [string[]]$Names) {
diff --git a/ci/run-unit-tests.ps1 b/ci/run-unit-tests.ps1
index 77ad8ca..e74a60f 100644
--- a/ci/run-unit-tests.ps1
+++ b/ci/run-unit-tests.ps1
@@ -3,5 +3,15 @@ param (
 )
 $ErrorActionPreference = "Stop"
 . (Join-Path $PSScriptRoot 'dispatch.ps1')
+. (Join-Path $PSScriptRoot 'packages.ps1')
+
+# Each package's tests take the packages it depends on from this checkout, so
+# they test the code those packages are released with. A tox.ini that takes
+# one from PyPI instead stops the tests before they run.
+$gaps = @(Get-ToxGaps (Split-Path $PSScriptRoot))
+if ($gaps.Count -gt 0) {
+    throw "A tox.ini takes a package from PyPI that this checkout has:`n" +
+        ($gaps -join "`n")
+}
 
 Invoke-ProductStep 'run-unit-tests' $RepoName $PSBoundParameters
diff --git a/device-detection/fiftyone_devicedetection_cloud/tox.ini b/device-detection/fiftyone_devicedetection_cloud/tox.ini
index 14fad03..a0d62c6 100644
--- a/device-detection/fiftyone_devicedetection_cloud/tox.ini
+++ b/device-detection/fiftyone_devicedetection_cloud/tox.ini
@@ -12,7 +12,13 @@ package = wheel
 wheel_build_env = .pkg
 deps =
     {[common]deps}
+    # The packages it depends on come from this checkout rather than a
+    # package index, so the tests run with the code they are released with.
     -e../fiftyone_devicedetection_shared/
+    -e../../pipeline/fiftyone_pipeline_core/
+    -e../../pipeline/fiftyone_pipeline_engines/
+    -e../../pipeline/fiftyone_pipeline_engines_fiftyone/
+    -e../../pipeline/fiftyone_pipeline_cloudrequestengine/
 commands =
     pytest --cov={envsitepackagesdir}/fiftyone_devicedetection_cloud {tty:--color=yes} {posargs}
 pass_env =
diff --git a/ip-intelligence/fiftyone_ipintelligence_cloud/tox.ini b/ip-intelligence/fiftyone_ipintelligence_cloud/tox.ini
index 4aa6341..668932c 100644
--- a/ip-intelligence/fiftyone_ipintelligence_cloud/tox.ini
+++ b/ip-intelligence/fiftyone_ipintelligence_cloud/tox.ini
@@ -12,7 +12,13 @@ package = wheel
 wheel_build_env = .pkg
 deps =
     {[common]deps}
+    # The packages it depends on come from this checkout rather than a
+    # package index, so the tests run with the code they are released with.
     -e../fiftyone_ipintelligence_shared/
+    -e../../pipeline/fiftyone_pipeline_core/
+    -e../../pipeline/fiftyone_pipeline_engines/
+    -e../../pipeline/fiftyone_pipeline_engines_fiftyone/
+    -e../../pipeline/fiftyone_pipeline_cloudrequestengine/
 commands =
     pytest --cov={envsitepackagesdir}/fiftyone_ipintelligence_cloud {tty:--color=yes} {posargs}
 pass_env =
diff --git a/ip-intelligence/fiftyone_ipintelligence_shared/tox.ini b/ip-intelligence/fiftyone_ipintelligence_shared/tox.ini
index 2bf335a..98972fd 100644
--- a/ip-intelligence/fiftyone_ipintelligence_shared/tox.ini
+++ b/ip-intelligence/fiftyone_ipintelligence_shared/tox.ini
@@ -12,6 +12,12 @@ package = wheel
 wheel_build_env = .pkg
 deps =
     {[common]deps}
+    # The packages it depends on come from this checkout rather than a
+    # package index, so the tests run with the code they are released with.
+    -e../../pipeline/fiftyone_pipeline_core/
+    -e../../pipeline/fiftyone_pipeline_engines/
+    -e../../pipeline/fiftyone_pipeline_engines_fiftyone/
+    -e../../pipeline/fiftyone_pipeline_cloudrequestengine/
 commands =
     pytest --cov={envsitepackagesdir}/fiftyone_ipintelligence_shared {tty:--color=yes} {posargs}
 pass_env =
diff --git a/ip-intelligence/fiftyone_ipintelligence_translation/tox.ini b/ip-intelligence/fiftyone_ipintelligence_translation/tox.ini
index 11283b9..b055ee0 100644
--- a/ip-intelligence/fiftyone_ipintelligence_translation/tox.ini
+++ b/ip-intelligence/fiftyone_ipintelligence_translation/tox.ini
@@ -12,6 +12,10 @@ package = wheel
 wheel_build_env = .pkg
 deps =
     {[common]deps}
+    # The packages it depends on come from this checkout rather than a
+    # package index, so the tests run with the code they are released with.
+    -e../../pipeline/fiftyone_pipeline_core/
+    -e../../pipeline/fiftyone_pipeline_translation/
 commands =
     pytest --cov={envsitepackagesdir}/fiftyone_ipintelligence_translation {tty:--color=yes} {posargs}
 pass_env =
diff --git a/location/tox.ini b/location/tox.ini
index 3cd28ff..504de88 100644
--- a/location/tox.ini
+++ b/location/tox.ini
@@ -8,6 +8,11 @@ wheel_build_env = .pkg
 deps =
     pytest>=6
     pytest-cov
+    # The packages it depends on come from this checkout rather than a
+    # package index, so the tests run with the code they are released with.
+    -e../pipeline/fiftyone_pipeline_core/
+    -e../pipeline/fiftyone_pipeline_engines/
+    -e../pipeline/fiftyone_pipeline_cloudrequestengine/
 commands =
     pytest --cov={envsitepackagesdir}/fiftyone_location {tty:--color=yes} {posargs}
 pass_env =