diff --git a/src/Runner.php b/src/Runner.php
index ffa3a5a..b7407cd 100644
--- a/src/Runner.php
+++ b/src/Runner.php
@@ -2,6 +2,9 @@
 
 namespace Migrator;
 
+use Migrator\Step\DynamicEnvironmentTrait;
+use Migrator\Step\StepParent;
+
 class Runner
 {
     use LoggerTrait;
@@ -40,8 +43,23 @@ public function __get($name)
     public function run()
     {
         foreach ($this->steps as $step) {
-            //determine if this is a step or an assertion
-            if (!empty($step['assertTrue']) || !empty($step['assertFalse'])) {
+
+          //determine if this is a step or an assertion or conditional
+            if($step['type'] == "conditional") {
+              // we determine if the condition is "true" - if so, we run the steps recursively
+              if(!isset($step['condition'])) {
+                  throw new \Exception(sprintf("Failed on step '%s' - no condition attached", $step['name']));
+              }
+
+              $condition = DynamicEnvironmentTrait::renderText($step['condition']);
+
+              if($condition == true) {
+                  $args = $this->args;
+                  $args->steps = $step['steps'];
+                  $runner = new Runner($args);
+                  $runner->run();
+              }
+            } else if (!empty($step['assertTrue']) || !empty($step['assertFalse'])) {
                 $this->runAssertion($step);
             } else {
                 $this->runStep($step);
diff --git a/src/Step/DynamicEnvironmentTrait.php b/src/Step/DynamicEnvironmentTrait.php
new file mode 100644
index 0000000..0048330
--- /dev/null
+++ b/src/Step/DynamicEnvironmentTrait.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace Migrator\Step;
+
+use function WyriHaximus\Twig\render;
+
+trait DynamicEnvironmentTrait {
+
+    static $dynamicEnvironment = [];
+
+    public static function fillDynamicEnvironmentFromEnv() {
+        $envVars = getenv();
+        foreach ($envVars as $key => $val) {
+            if($key == "JSON_PAYLOAD") {
+                self::fillDynamicEnvironmentFromJSONPayload($val);
+            } else {
+                self::setVariable(sprintf("%s", $key), $val);
+            }
+
+        }
+    }
+
+    public static function fillDynamicEnvironmentFromJSONPayload($payload) {
+
+        $decodedJson = base64_decode($payload);
+        if(!$decodedJson) {
+            throw new \Exception("Found JSON_PAYLOAD but could not decode it");
+        }
+
+        $vars = json_decode($decodedJson, true);
+
+        if(json_last_error() > 0) {
+            throw new \Exception(sprintf("Could not decode JSONPAYLOAD: %s ", json_last_error_msg()));
+        }
+
+        foreach ($vars as $key => $val) {
+            self::setVariable($key, $val);
+        }
+    }
+
+    public static function setVariable($name, $value) {
+        self::$dynamicEnvironment[$name] = $value;
+    }
+
+    public static function getVariable($name) {
+        if(!key_exists($name, self::$dynamicEnvironment)) {
+            throw new \Exception("Unable to find variable {$name} in dynamic environment - have you previously set it?");
+        }
+        return self::$dynamicEnvironment[$name];
+    }
+
+    public static function getAllVariables() {
+        return self::$dynamicEnvironment;
+    }
+
+    public static function renderText($template, $extraVars = [])
+    {
+        $subs = array_merge(self::getAllVariables(), $extraVars);
+        return render($template, $subs);
+    }
+
+}
diff --git a/src/Step/StepParent.php b/src/Step/StepParent.php
index 397d37a..c4d4928 100644
--- a/src/Step/StepParent.php
+++ b/src/Step/StepParent.php
@@ -12,7 +12,7 @@
 
 abstract class StepParent implements StepInterface
 {
-    use LoggerTrait;
+    use LoggerTrait, DynamicEnvironmentTrait;
     protected $cluster;
     protected $namespace;
     protected $utilityBelt;
@@ -20,54 +20,6 @@ abstract class StepParent implements StepInterface
     protected $args;
     protected $commandName;
 
-    static $dynamicEnvironment = [];
-
-
-    public static function fillDynamicEnvironmentFromEnv() {
-      $envVars = getenv();
-      foreach ($envVars as $key => $val) {
-        if($key == "JSON_PAYLOAD") {
-          self::fillDynamicEnvironmentFromJSONPayload($val);
-        } else {
-          self::setVariable(sprintf("%s", $key), $val);
-        }
-
-      }
-    }
-
-    public static function fillDynamicEnvironmentFromJSONPayload($payload) {
-
-      $decodedJson = base64_decode($payload);
-      if(!$decodedJson) {
-        throw new \Exception("Found JSON_PAYLOAD but could not decode it");
-      }
-
-      $vars = json_decode($decodedJson, true);
-
-      if(json_last_error() > 0) {
-        throw new \Exception(sprintf("Could not decode JSONPAYLOAD: %s ", json_last_error_msg()));
-      }
-
-      foreach ($vars as $key => $val) {
-        self::setVariable($key, $val);
-      }
-    }
-
-    public static function setVariable($name, $value) {
-            self::$dynamicEnvironment[$name] = $value;
-    }
-
-    public static function getVariable($name) {
-        if(!key_exists($name, self::$dynamicEnvironment)) {
-            throw new \Exception("Unable to find variable {$name} in dynamic environment - have you previously set it?");
-        }
-        return self::$dynamicEnvironment[$name];
-    }
-
-    public static function getAllVariables() {
-        return self::$dynamicEnvironment;
-    }
-
     public function __construct(LagoonUtilityBeltInterface $utilityBelt, RunnerArgs $args)
     {
         $this->cluster = $args->cluster;
@@ -106,19 +58,13 @@ public function run(array $args) {
    */
   public function doTextSubstitutions($string)
   {
-    $substitutions = [
+    $extraSubs = [
       'project' => $this->args->project,
       'environment' => $this->args->environment,
       'namespace' => $this->args->namespace,
     ];
 
-    //Here we reach into the dynamic environment to grab any other arbitrarily defined vars
-    foreach (self::getAllVariables() as $key => $value) {
-      $substitutions[$key] =  $value;
-    }
-
-
-    return render($string, $substitutions);
+      return self::renderText($string, $extraSubs);
   }
 
     // We use dynamic dispatch to allow us to do some logging and
diff --git a/src/Step/Test.php b/src/Step/Test.php
index 9a69da5..75fc85b 100644
--- a/src/Step/Test.php
+++ b/src/Step/Test.php
@@ -6,10 +6,28 @@
 
 class Test extends StepParent {
 
+    public static $callbacks = [];
+
+    public static function setCallback(callable $cb)
+    {
+        self::$callbacks[] = $cb;
+    }
+
+    public static function clearCallbacks()
+    {
+        self::$callbacks = [];
+    }
+
     public function runImplementation(array $args)
     {
-        //check we have all the args we need
-        //TODO: can be used to test things - will be removed
+        // check we have all the args we need
+        // we just run through all the registered callbacks and call them with the args
+        // This allows tests to attach their functions
+        foreach (self::$callbacks as $callback) {
+            if(is_callable($callback)) {
+               $callback($args);
+            }
+        }
     }
 
 }
\ No newline at end of file
diff --git a/tests/DeployTest.php b/tests/DeployTest.php
index d4a5651..1f78387 100644
--- a/tests/DeployTest.php
+++ b/tests/DeployTest.php
@@ -48,7 +48,7 @@ public function testStandardTextualSubstitutionsInArgs() {
 
     // Here we replace LAGOON_BACKUPS_DISABLED with whatever is
     // placed into the dynamic environment
-    $buildVars = ['LAGOON_BACKUPS_DISABLED', '{{ LAGOON_BACKUPS_DISABLED }}'];
+    $buildVars = [["name" => 'LAGOON_BACKUPS_DISABLED', "value"=>'{{ LAGOON_BACKUPS_DISABLED }}']];
 
     $args = [
       'project' => 'testproject',
@@ -58,7 +58,7 @@ public function testStandardTextualSubstitutionsInArgs() {
     ];
 
     // Once the textual subs for $buildVars is done, we expect the following...
-    $buildWithSubs = ['LAGOON_BACKUPS_DISABLED', 'false'];
+    $buildWithSubs = [["name" => 'LAGOON_BACKUPS_DISABLED', "value"=>'false']];
 
     $lub->expects($this->once())
       ->method("deployEnvironment")
diff --git a/tests/RunnerTest.php b/tests/RunnerTest.php
new file mode 100644
index 0000000..f9a4ca4
--- /dev/null
+++ b/tests/RunnerTest.php
@@ -0,0 +1,137 @@
+<?php
+
+use Migrator\Runner;
+use PHPUnit\Framework\TestCase;
+
+class RunnerTest extends TestCase
+{
+
+    protected function getStepsFromFile($filename)
+    {
+        return \Symfony\Component\Yaml\Yaml::parse(
+          file_get_contents($filename)
+        );
+    }
+
+    /**
+     * This test will simply check that the runner works generally
+     *
+     * @return void
+     */
+    function testBasicCase()
+    {
+        //just testing the test case callback
+        $testRan = false;
+        $cb = function ($args) use (&$testRan) {
+            $testRan = true;
+        };
+        \Migrator\Step\Test::setCallback($cb);
+
+        $steps = $this->getStepsFromFile(
+          __DIR__ . "/assets/RunnerTestBasicCase.yaml"
+        );
+        $args = new \Migrator\RunnerArgs();
+        $args->steps = $steps['steps'];
+        $runner = new \Migrator\Runner($args);
+        $runner->run();
+        $this->assertTrue($testRan);
+        \Migrator\Step\Test::clearCallbacks();
+    }
+
+    /**
+     * This drives/tests the conditional system - basic conditional
+     * Further tests will work on textual substitutions etc.
+     *
+     * @return void
+     */
+    function testConditionalRun()
+    {
+        //just testing the test case callback
+        $conditionalStepRan = false;
+        $cb = function ($args) use (&$conditionalStepRan) {
+            if(!empty($args['testid']) && $args['testid'] == 1)
+            {
+                $conditionalStepRan = true;
+            }
+        };
+        \Migrator\Step\Test::setCallback($cb);
+
+        $steps = $this->getStepsFromFile(
+          __DIR__ . "/assets/RunnerTestConditionalRun.yaml"
+        );
+        $args = new \Migrator\RunnerArgs();
+        $args->steps = $steps['steps'];
+        $runner = new \Migrator\Runner($args);
+        $runner->run();
+        $this->assertTrue($conditionalStepRan);
+        \Migrator\Step\Test::clearCallbacks();
+    }
+
+    /**
+     * This drives/tests the conditional system - basic conditional
+     * Further tests will work on textual substitutions etc.
+     *
+     * @return void
+     */
+    function testConditionalDidntRun()
+    {
+        //just testing the test case callback
+        $conditionalStepRan = false;
+        $cb = function ($args) use (&$conditionalStepRan) {
+            if(!empty($args['testid']) && $args['testid'] == 1)
+            {
+                $conditionalStepRan = true;
+            }
+        };
+        \Migrator\Step\Test::setCallback($cb);
+
+        $steps = $this->getStepsFromFile(
+          __DIR__ . "/assets/RunnerTestConditionalDidntRun.yaml"
+        );
+        $args = new \Migrator\RunnerArgs();
+        $args->steps = $steps['steps'];
+        $runner = new \Migrator\Runner($args);
+        $runner->run();
+        $this->assertFalse($conditionalStepRan);
+        \Migrator\Step\Test::clearCallbacks();
+    }
+
+    /**
+     * This drives/tests the conditional system - basic conditional
+     * Further tests will work on textual substitutions etc.
+     *
+     * @return void
+     */
+    function testConditionalWithTwigConditions()
+    {
+        //just testing the test case callback
+        $conditionalStepShouldHaveRun = false;
+        \Migrator\Step\DynamicEnvironmentTrait::setVariable('RUN_THIS', "true");
+        \Migrator\Step\DynamicEnvironmentTrait::setVariable('DONT_RUN_THAT', "true");
+        $conditionalStepShouldNotHaveRun = true;
+        $cb = function ($args) use (&$conditionalStepShouldHaveRun, &$conditionalStepShouldNotHaveRun) {
+            if(!empty($args['testid']) && $args['testid'] == 1)
+            {
+                $conditionalStepShouldHaveRun = true;
+            }
+            if(!empty($args['testid']) && $args['testid'] == 2)
+            {
+                $conditionalStepShouldNotHaveRun = false;
+            }
+        };
+        \Migrator\Step\Test::setCallback($cb);
+
+        $steps = $this->getStepsFromFile(
+          __DIR__ . "/assets/RunnerTestConditionalTwig.yaml"
+        );
+        $args = new \Migrator\RunnerArgs();
+        $args->steps = $steps['steps'];
+        $runner = new \Migrator\Runner($args);
+        $runner->run();
+        $this->assertTrue($conditionalStepShouldHaveRun);
+        $this->assertTrue($conditionalStepShouldNotHaveRun);
+
+        \Migrator\Step\Test::clearCallbacks();
+    }
+
+}
diff --git a/tests/assets/RunnerTestBasicCase.yaml b/tests/assets/RunnerTestBasicCase.yaml
new file mode 100644
index 0000000..e567ed2
--- /dev/null
+++ b/tests/assets/RunnerTestBasicCase.yaml
@@ -0,0 +1,3 @@
+steps:
+  - name: basic run test
+    type: test
\ No newline at end of file
diff --git a/tests/assets/RunnerTestConditionalDidntRun.yaml b/tests/assets/RunnerTestConditionalDidntRun.yaml
new file mode 100644
index 0000000..3115888
--- /dev/null
+++ b/tests/assets/RunnerTestConditionalDidntRun.yaml
@@ -0,0 +1,10 @@
+steps:
+  - name: basic run test
+    type: test
+  - name: conditional will always run
+    type: conditional
+    condition: false
+    steps:
+      - name: conditional first level
+        type: test
+        testid: 1
\ No newline at end of file
diff --git a/tests/assets/RunnerTestConditionalRun.yaml b/tests/assets/RunnerTestConditionalRun.yaml
new file mode 100644
index 0000000..9ac71c5
--- /dev/null
+++ b/tests/assets/RunnerTestConditionalRun.yaml
@@ -0,0 +1,10 @@
+steps:
+  - name: basic run test
+    type: test
+  - name: conditional will always run
+    type: conditional
+    condition: true
+    steps:
+      - name: conditional first level
+        type: test
+        testid: 1
\ No newline at end of file
diff --git a/tests/assets/RunnerTestConditionalTwig.yaml b/tests/assets/RunnerTestConditionalTwig.yaml
new file mode 100644
index 0000000..f54bdc2
--- /dev/null
+++ b/tests/assets/RunnerTestConditionalTwig.yaml
@@ -0,0 +1,17 @@
+steps:
+  - name: basic run test
+    type: test
+  - name: conditional will run if RUN_THIS is set to true
+    type: conditional
+    condition: '{{ RUN_THIS == "true" ? true : false }}'
+    steps:
+      - name: conditional first level
+        type: test
+        testid: 1
+  - name: conditional will run if DONT_RUN_THAT is set to false
+    type: conditional
+    condition: '{{ DONT_RUN_THAT == "false" ? true : false }}'
+    steps:
+      - name: conditional first level
+        type: test
+        testid: 2
\ No newline at end of file