diff --git a/azure/stages.yml b/azure/stages.yml
index ede925f..15f3444 100644
--- a/azure/stages.yml
+++ b/azure/stages.yml
@@ -10,6 +10,7 @@ parameters:
   check_all_features: true
   nightly_feature: ''
   test_features: ''
+  test_arguments: '--' # Defaults to a separator
 
 stages:
  # the format here is so that we can have _two_ instances of this whole
@@ -58,6 +59,7 @@ stages:
          single_threaded: ${{ parameters.single_threaded }}
          nightly_feature: ${{ parameters.nightly_feature }}
          features: ${{ parameters.test_features }}
+         arguments: ${{ parameters.test_arguments }}
  - stage: ${{ format('{0}style', parameters.prefix) }}
    ${{ if ne(parameters.prefix, '') }}:
      displayName: ${{ format('Style linting ({0})', parameters.prefix) }}
diff --git a/azure/test.yml b/azure/test.yml
index 47cedfe..1b5fb38 100644
--- a/azure/test.yml
+++ b/azure/test.yml
@@ -7,6 +7,7 @@ parameters:
   test_ignored: false
   single_threaded: false
   features: '' # empty feature list is == default
+  arguments: '--' # Defaults to the separator between cargo opts and libtest opts
 
 jobs:
 - job: ${{ parameters.name }}
@@ -24,9 +25,11 @@ jobs:
           vmImage: macOS-10.14
         Windows:
           vmImage: windows-2019
-  ${{ if ne('true', parameters.cross) }}:
-    variables:
+  variables:
+    ${{ if ne('true', parameters.cross) }}:
       vmImage: ubuntu-16.04
+    cargo_opts: ''
+    libtest_opts: ''
   pool:
     vmImage: $(vmImage)
   steps:
@@ -34,23 +37,21 @@ jobs:
     parameters:
       rust: ${{ parameters.rust }}
       setup: ${{ parameters.setup }}
-  - ${{ if ne('true', parameters.single_threaded) }}:
-    - script: cargo test --all --features "${{ parameters.features }}"
-      displayName: Run tests
-      env:
-        ${{ insert }}: ${{ parameters.envs }}
+  # Cargo options go here
+  - bash: echo '##vso[task.setvariable variable=cargo_opts]$(cargo_opts) --all'
+  - ${{ if eq(true, parameters.features)}}:
+    - bash: echo '##vso[task.setvariable variable=cargo_opts]$(cargo_opts) --features "${{ parameters.features }}"'
+  # Libtest options go here
   - ${{ if eq('true', parameters.single_threaded) }}:
-    - script: cargo test --all --features "${{ parameters.features }}" -- --test-threads=1
-      displayName: Run tests (single-threaded)
-      env:
-        ${{ insert }}: ${{ parameters.envs }}
-  - ${{ if and(eq('true', parameters.test_ignored), ne('true', parameters.single_threaded)) }}:
-    - script: cargo test --all --features "${{ parameters.features }}" -- --ignored
+    - bash: echo '##vso[task.setvariable variable=libtest_opts]$(libtest_opts) --test-threads=1'
+  # Run tests with the given options
+  - bash: cargo test $(cargo_opts) ${{ parameters.arguments }} $(libtest_opts)
+    displayName: Run tests
+    env:
+      ${{ insert }}: ${{ parameters.envs }}
+  - ${{ if eq('true', parameters.test_ignored)}}:
+    - bash: cargo test $(cargo_opts) ${{ parameters.arguments }} $(libtest_opts) --ignored
       displayName: Run ignored tests
       env:
         ${{ insert }}: ${{ parameters.envs }}
-  - ${{ if and(eq('true', parameters.test_ignored), eq('true', parameters.single_threaded)) }}:
-    - script: cargo test --all --features "${{ parameters.features }}" -- --ignored --test-threads=1
-      displayName: Run ignored tests (single-threaded)
-      env:
-        ${{ insert }}: ${{ parameters.envs }}
+
diff --git a/azure/tests.yml b/azure/tests.yml
index bbab2de..0560a76 100644
--- a/azure/tests.yml
+++ b/azure/tests.yml
@@ -5,6 +5,7 @@ parameters:
   single_threaded: false
   nightly_feature: ''
   features: ''
+  arguments: '--'
 
 jobs:
  - template: test.yml
@@ -16,6 +17,7 @@ jobs:
      test_ignored: ${{ parameters.test_ignored }}
      single_threaded: ${{ parameters.single_threaded }}
      features: ${{ parameters.features }}
+     arguments: ${{ parameters.arguments }}
  - template: test.yml
    parameters:
      name: cargo_test_beta
@@ -25,6 +27,7 @@ jobs:
      test_ignored: ${{ parameters.test_ignored }}
      single_threaded: ${{ parameters.single_threaded }}
      features: ${{ parameters.features }}
+     arguments: ${{ parameters.arguments }}
  - template: test.yml
    parameters:
      name: cargo_test_nightly
@@ -35,3 +38,4 @@ jobs:
      test_ignored: ${{ parameters.test_ignored }}
      single_threaded: ${{ parameters.single_threaded }}
      features: "${{ parameters.features }},${{ parameters.nightly_feature }}"
+     arguments: ${{ parameters.arguments }}
diff --git a/docs/configuration.md b/docs/configuration.md
index 3aefd15..3a32f17 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -101,6 +101,26 @@ fashion](https://doc.rust-lang.org/book/ch11-02-running-tests.html#running-tests
 case for you, set this parameter to `true` and your tests will be run
 with `--test-threads=1`.
 
+### Custom Arguments
+
+```yaml
+stages:
+ - template: azure/stages.yml@templates
+   parameters:
+     test_arguments: <string> = '--'
+```
+
+If the pre-baked `cargo test` parameters are not extensible enough for your
+use case, (for example, if you need to pass unstable `-Z` options) you can
+pass `cargo test` custom arguments that are used *in addition* to any others
+set by parameters. This parameter has a syntax:
+
+`<cargo test args> -- <libtest args>`
+
+Note that even if you include no libtest arguments, you must still include
+a trailing `--` so that any libtest arguments passed by other
+configuration options (such as `single_threaded`) will still work correctly.
+
 ### Disable checking all features
 
 ```yaml
diff --git a/docs/custom.md b/docs/custom.md
index 2ce27c0..0fb2853 100644
--- a/docs/custom.md
+++ b/docs/custom.md
@@ -160,7 +160,7 @@ to run [additional setup
 steps](configuration.md#additional-setup-steps). You can also pass
 `features` and/or `nightly_feature` to include additional cargo features
 when running the tests. `nightly_feature` will only be included on runs
-with the nightly compiler. See the [test docs](#test) for details.
+with the nightly compiler. See the [test docs](#test) for details. 
 
 ### Test
 
@@ -173,6 +173,7 @@ parameters:
   test_ignored: <bool> = false
   single_threaded: <bool> = false
   features: <string> = ''
+  arguments: <string> = '--'
   envs:
     NAME: value
   setup:
@@ -192,6 +193,7 @@ set `test_ignored: true`. To run tests with
 [`--test-threads=1`](https://doc.rust-lang.org/book/ch11-02-running-tests.html#running-tests-in-parallel-or-consecutively),
 set `single_threaded: true`. To run tests with particular features
 enabled, pass `features: "feat1,feat2,subcrate/feat3"`.
+To include arbitrary `cargo test` arguments, pass `arguments: <test args -- libtest args>`, but note that you must always include the `--`, even if you add no libtest args.
 
 ### Style