diff --git a/src/Chances/Chance.php b/src/Chances/Chance.php
index 0af2cc0..79cd8cd 100644
--- a/src/Chances/Chance.php
+++ b/src/Chances/Chance.php
@@ -1,7 +1,9 @@
 <?php
+declare(strict_types=1);
+
 namespace Scientist\Chances;
 
 interface Chance
 {
-    public function shouldRun();
+    public function shouldRun(): bool;
 }
diff --git a/src/Chances/StandardChance.php b/src/Chances/StandardChance.php
index 8b08cd7..3b6321b 100644
--- a/src/Chances/StandardChance.php
+++ b/src/Chances/StandardChance.php
@@ -1,14 +1,19 @@
 <?php
+declare(strict_types=1);
+
 namespace Scientist\Chances;
 
 class StandardChance implements Chance
 {
+    /**
+     * @var int
+     */
     private $percentage = 100;
 
     /**
      * Determine whether or not the experiment should run
      */
-    public function shouldRun()
+    public function shouldRun(): bool
     {
         if ($this->percentage == 0) {
             return false;
@@ -19,19 +24,12 @@ public function shouldRun()
         return $random <= $this->percentage;
     }
 
-    /**
-     * @return int
-     */
-    public function getPercentage()
+    public function getPercentage(): int
     {
         return $this->percentage;
     }
 
-    /**
-     * @param int $percentage
-     * @return $this
-     */
-    public function setPercentage($percentage)
+    public function setPercentage(int $percentage): self
     {
         $this->percentage = $percentage;
         
diff --git a/src/Experiment.php b/src/Experiment.php
index 741a1d1..aa0c0d6 100644
--- a/src/Experiment.php
+++ b/src/Experiment.php
@@ -1,7 +1,9 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist;
 
+use Scientist\Report;
 use Scientist\Chances\Chance;
 use Scientist\Chances\StandardChance;
 use Scientist\Matchers\Matcher;
@@ -41,7 +43,7 @@ class Experiment
     /**
      * Trial callbacks.
      *
-     * @var array
+     * @var callable[]
      */
     protected $trials = [];
 
@@ -75,11 +77,8 @@ class Experiment
 
     /**
      * Create a new experiment.
-     *
-     * @param string                $name
-     * @param \Scientist\Laboratory $laboratory
      */
-    public function __construct($name, Laboratory $laboratory)
+    public function __construct(string $name, Laboratory $laboratory)
     {
         $this->name = $name;
         $this->laboratory = $laboratory;
@@ -89,20 +88,16 @@ public function __construct($name, Laboratory $laboratory)
 
     /**
      * Fetch the experiment name.
-     *
-     * @return string
      */
-    public function getName()
+    public function getName(): string
     {
         return $this->name;
     }
 
     /**
      * Retrieve the laboratory instance.
-     *
-     * @return \Scientist\Laboratory|null
      */
-    public function getLaboratory()
+    public function getLaboratory(): ?Laboratory
     {
         return $this->laboratory;
     }
@@ -110,12 +105,9 @@ public function getLaboratory()
     /**
      * Register a control callback.
      *
-     * @param callable $callback
      * @param mixed $context
-     *
-     * @return $this
      */
-    public function control(callable $callback, $context = null)
+    public function control(callable $callback, $context = null): self
     {
         $this->control = $callback;
         $this->controlContext = $context;
@@ -125,14 +117,15 @@ public function control(callable $callback, $context = null)
 
     /**
      * Fetch the control callback.
-     *
-     * @return callable
      */
-    public function getControl()
+    public function getControl(): callable
     {
         return $this->control;
     }
 
+    /**
+     * @return mixed
+     */
     public function getControlContext()
     {
         return $this->controlContext;
@@ -141,12 +134,9 @@ public function getControlContext()
     /**
      * Register a trial callback.
      *
-     * @param string   $name
-     * @param callable $callback
-     *
-     * @return $this
+     * @param mixed $context
      */
-    public function trial($name, callable $callback, $context = null)
+    public function trial(string $name, callable $callback, $context = null): self
     {
         $this->trials[$name] = new Trial($name, $callback, $context);
 
@@ -155,12 +145,8 @@ public function trial($name, callable $callback, $context = null)
 
     /**
      * Fetch a trial callback by name.
-     *
-     * @param string $name
-     *
-     * @return mixed
      */
-    public function getTrial($name)
+    public function getTrial(string $name): callable
     {
         return $this->trials[$name]->getCallback();
     }
@@ -168,21 +154,17 @@ public function getTrial($name)
     /**
      * Fetch an array of trial callbacks.
      *
-     * @return array
+     * @return callable[]
      */
-    public function getTrials()
+    public function getTrials(): array
     {
         return $this->trials;
     }
 
     /**
      * Set a matcher for this experiment.
-     *
-     * @param \Scientist\Matchers\Matcher $matcher
-     *
-     * @return $this
      */
-    public function matcher(Matcher $matcher)
+    public function matcher(Matcher $matcher): self
     {
         $this->matcher = $matcher;
 
@@ -191,22 +173,16 @@ public function matcher(Matcher $matcher)
 
     /**
      * Get the matcher for this experiment.
-     *
-     * @return \Scientist\Matchers\Matcher
      */
-    public function getMatcher()
+    public function getMatcher(): Matcher
     {
         return $this->matcher;
     }
 
     /**
      * Set the execution chance.
-     *
-     * @param Chances\Chance $chance
-     *
-     * @return $this
      */
-    public function chance(Chance $chance)
+    public function chance(Chance $chance): self
     {
         $this->chance = $chance;
 
@@ -215,20 +191,16 @@ public function chance(Chance $chance)
 
     /**
      * Get the execution chance.
-     *
-     * @return Chances\Chance
      */
-    public function getChance()
+    public function getChance(): Chance
     {
         return $this->chance;
     }
 
     /**
      * Determine whether an experiment should run based on chance.
-     *
-     * @return boolean
      */
-    public function shouldRun()
+    public function shouldRun(): bool
     {
         return $this->chance
             ->shouldRun();
@@ -236,10 +208,8 @@ public function shouldRun()
 
     /**
      * Get the experiment parameters.
-     *
-     * @return array
      */
-    public function getParams()
+    public function getParams(): array
     {
         return $this->params;
     }
@@ -258,10 +228,8 @@ public function run()
 
     /**
      * Execute the experiment and return a report.
-     *
-     * @return \Scientist\Report
      */
-    public function report()
+    public function report(): Report
     {
         $this->params = func_get_args();
 
diff --git a/src/Intern.php b/src/Intern.php
index 44091b4..986367d 100644
--- a/src/Intern.php
+++ b/src/Intern.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist;
 
@@ -16,12 +17,8 @@ class Intern
 {
     /**
      * Run an experiment, and retrieve the result.
-     *
-     * @param \Scientist\Experiment $experiment
-     *
-     * @return \Scientist\Report
      */
-    public function run(Experiment $experiment)
+    public function run(Experiment $experiment): Report
     {
         $control = $this->runControl($experiment);
         $trials  = $this->runTrials($experiment);
@@ -33,12 +30,8 @@ public function run(Experiment $experiment)
 
     /**
      * Run the control callback, and record its execution state.
-     *
-     * @param \Scientist\Experiment $experiment
-     *
-     * @return \Scientist\Result
      */
-    protected function runControl(Experiment $experiment)
+    protected function runControl(Experiment $experiment): Result
     {
         return (new Machine(
             $experiment->getControl(),
@@ -51,11 +44,9 @@ protected function runControl(Experiment $experiment)
     /**
      * Run trial callbacks and record their execution state.
      *
-     * @param \Scientist\Experiment $experiment
-     *
-     * @return \Scientist\Result[]
+     * @return Result[]
      */
-    protected function runTrials(Experiment $experiment)
+    protected function runTrials(Experiment $experiment): array
     {
         $executions = [];
 
@@ -74,11 +65,9 @@ protected function runTrials(Experiment $experiment)
     /**
      * Determine whether trial results match the control.
      *
-     * @param \Scientist\Matchers\Matcher $matcher
-     * @param \Scientist\Result           $control
-     * @param \Scientist\Result[]         $trials
+     * @param Result[] $trials
      */
-    protected function determineMatches(Matcher $matcher, Result $control, array $trials = [])
+    protected function determineMatches(Matcher $matcher, Result $control, array $trials = []): void
     {
         foreach ($trials as $trial) {
             if ($matcher->match($control->getValue(), $trial->getValue())) {
diff --git a/src/Journals/Journal.php b/src/Journals/Journal.php
index 7b8151f..87b7299 100644
--- a/src/Journals/Journal.php
+++ b/src/Journals/Journal.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist\Journals;
 
@@ -18,9 +19,6 @@ interface Journal
     /**
      * Dispatch a report to storage.
      *
-     * @param \Scientist\Experiment $experiment
-     * @param \Scientist\Report     $report
-     *
      * @return mixed
      */
     public function report(Experiment $experiment, Report $report);
diff --git a/src/Journals/StandardJournal.php b/src/Journals/StandardJournal.php
index 94977e6..fe41459 100644
--- a/src/Journals/StandardJournal.php
+++ b/src/Journals/StandardJournal.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist\Journals;
 
@@ -15,26 +16,21 @@ class StandardJournal implements Journal
     /**
      * The executed experiment.
      *
-     * @var \Scientist\Experiment
+     * @var Experiment
      */
     protected $experiment;
 
     /**
      * The experiment report.
      *
-     * @var \Scientist\Report
+     * @var Report
      */
     protected $report;
 
     /**
      * Dispatch a report to storage.
-     *
-     * @param \Scientist\Experiment $experiment
-     * @param \Scientist\Report     $report
-     *
-     * @return mixed
      */
-    public function report(Experiment $experiment, Report $report)
+    public function report(Experiment $experiment, Report $report): void
     {
         $this->experiment = $experiment;
         $this->report     = $report;
@@ -42,20 +38,16 @@ public function report(Experiment $experiment, Report $report)
 
     /**
      * Get the experiment.
-     *
-     * @return \Scientist\Experiment
      */
-    public function getExperiment()
+    public function getExperiment(): Experiment
     {
         return $this->experiment;
     }
 
     /**
      * Get the experiment report.
-     *
-     * @return \Scientist\Report
      */
-    public function getReport()
+    public function getReport(): Report
     {
         return $this->report;
     }
diff --git a/src/Laboratory.php b/src/Laboratory.php
index 489ad28..f32a2dd 100644
--- a/src/Laboratory.php
+++ b/src/Laboratory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist;
 
@@ -24,11 +25,9 @@ class Laboratory
     /**
      * Register a collection of journals.
      *
-     * @param array $journals
-     *
-     * @return $this
+     * @param Journal[] $journals
      */
-    public function setJournals(array $journals = [])
+    public function setJournals(array $journals = []): self
     {
         $this->journals = [];
         foreach ($journals as $journal) {
@@ -40,12 +39,8 @@ public function setJournals(array $journals = [])
 
     /**
      * Register a new journal.
-     *
-     * @param \Scientist\Journals\Journal $journal
-     *
-     * @return $this
      */
-    public function addJournal(Journal $journal)
+    public function addJournal(Journal $journal): self
     {
         $this->journals[] = $journal;
 
@@ -55,9 +50,9 @@ public function addJournal(Journal $journal)
     /**
      * Retrieve registers journals.
      *
-     * @return array
+     * @return Journal[]
      */
-    public function getJournals()
+    public function getJournals(): array
     {
         return $this->journals;
     }
@@ -65,11 +60,9 @@ public function getJournals()
     /**
      * Start a new experiment.
      *
-     * @param string $name
-     *
      * @return mixed
      */
-    public function experiment($name)
+    public function experiment(string $name)
     {
         return (new Experiment($name, $this));
     }
@@ -77,8 +70,6 @@ public function experiment($name)
     /**
      * Run an experiment.
      *
-     * @param \Scientist\Experiment $experiment
-     *
      * @return mixed
      */
     public function runExperiment(Experiment $experiment)
@@ -96,12 +87,8 @@ public function runExperiment(Experiment $experiment)
 
     /**
      * Run an experiment and return the result.
-     *
-     * @param \Scientist\Experiment $experiment
-     *
-     * @return \Scientist\Report
      */
-    public function getReport(Experiment $experiment)
+    public function getReport(Experiment $experiment): Report
     {
         $report = (new Intern)->run($experiment);
         $this->reportToJournals($experiment, $report);
@@ -111,13 +98,8 @@ public function getReport(Experiment $experiment)
 
     /**
      * Report experiment result to registered journals.
-     *
-     * @param \Scientist\Experiment $experiment
-     * @param \Scientist\Report     $report
-     *
-     * @return void
      */
-    protected function reportToJournals(Experiment $experiment, Report $report)
+    protected function reportToJournals(Experiment $experiment, Report $report): void
     {
         foreach ($this->journals as $journal) {
             $journal->report($experiment, $report);
diff --git a/src/Machine.php b/src/Machine.php
index 8277b3a..1760c28 100644
--- a/src/Machine.php
+++ b/src/Machine.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist;
 
@@ -28,7 +29,7 @@ class Machine
     /**
      * Should exceptions be muted.
      *
-     * @var boolean
+     * @var bool
      */
     protected $muted = false;
 
@@ -42,11 +43,9 @@ class Machine
     /**
      * Inject machine dependencies.
      *
-     * @param callable $callback
-     * @param array    $params
-     * @param boolean  $muted
+     * @param mixed $context
      */
-    public function __construct(callable $callback, array $params = [], $muted = false, $context = null)
+    public function __construct(callable $callback, array $params = [], bool $muted = false, $context = null)
     {
         $this->callback = $callback;
         $this->params   = $params;
@@ -56,10 +55,8 @@ public function __construct(callable $callback, array $params = [], $muted = fal
 
     /**
      * Execute the callback and retrieve a result.
-     *
-     * @return \Scientist\Result
      */
-    public function execute()
+    public function execute(): Result
     {
         $this->setStartValues();
         $this->executeCallback();
@@ -70,10 +67,8 @@ public function execute()
 
     /**
      * Set values before callback is executed.
-     *
-     * @return void
      */
-    protected function setStartValues()
+    protected function setStartValues(): void
     {
         $this->result->setStartTime(microtime(true));
         $this->result->setStartMemory(memory_get_usage());
@@ -81,13 +76,12 @@ protected function setStartValues()
 
     /**
      * Execute the callback with parameters.
-     *
-     * @return void
      */
-    protected function executeCallback()
+    protected function executeCallback(): void
     {
         if ($this->muted) {
-            return $this->executeMutedCallback();
+            $this->executeMutedCallback();
+            return;
         }
 
         $this->result->setValue(call_user_func_array($this->callback, $this->params));
@@ -95,14 +89,12 @@ protected function executeCallback()
 
     /**
      * Execute the callback, but swallow exceptions.
-     *
-     * @return void
      */
-    protected function executeMutedCallback()
+    protected function executeMutedCallback(): void
     {
         try {
             $this->result->setValue(call_user_func_array($this->callback, $this->params));
-        } catch (Throwable $exception) {
+        } catch (\Throwable $exception) {
             $this->result->setException($exception);
             $this->result->setValue(null);
         }
@@ -110,10 +102,8 @@ protected function executeMutedCallback()
 
     /**
      * Set values after the callback has executed.
-     *
-     * @return void
      */
-    protected function setEndValues()
+    protected function setEndValues(): void
     {
         $this->result->setEndTime(microtime(true));
         $this->result->setEndMemory(memory_get_usage());
diff --git a/src/Matchers/ClosureMatcher.php b/src/Matchers/ClosureMatcher.php
index 9069f73..37fe5c3 100644
--- a/src/Matchers/ClosureMatcher.php
+++ b/src/Matchers/ClosureMatcher.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist\Matchers;
 
@@ -17,7 +18,6 @@ class ClosureMatcher implements Matcher
 
     /**
      * Create a new matcher instance based on a closure.
-     * @param \Closure $closure The closure to use
      */
     public function __construct(\Closure $closure)
     {
@@ -27,7 +27,7 @@ public function __construct(\Closure $closure)
     /**
      * @inheritDoc
      */
-    public function match($control, $trial)
+    public function match($control, $trial): bool
     {
         return call_user_func($this->closure, $control, $trial);
     }
diff --git a/src/Matchers/Matcher.php b/src/Matchers/Matcher.php
index 7e8fb3a..45dbeec 100644
--- a/src/Matchers/Matcher.php
+++ b/src/Matchers/Matcher.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist\Matchers;
 
@@ -16,8 +17,6 @@ interface Matcher
      *
      * @param mixed $control
      * @param mixed $trial
-     *
-     * @return boolean
      */
-    public function match($control, $trial);
+    public function match($control, $trial): bool;
 }
diff --git a/src/Matchers/StandardMatcher.php b/src/Matchers/StandardMatcher.php
index a560377..f9e7478 100644
--- a/src/Matchers/StandardMatcher.php
+++ b/src/Matchers/StandardMatcher.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist\Matchers;
 
@@ -14,10 +15,8 @@ class StandardMatcher implements Matcher
      *
      * @param mixed $control
      * @param mixed $trial
-     *
-     * @return boolean
      */
-    public function match($control, $trial)
+    public function match($control, $trial): bool
     {
         return $control === $trial;
     }
diff --git a/src/Report.php b/src/Report.php
index fba2b5d..25b3094 100644
--- a/src/Report.php
+++ b/src/Report.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist;
 
@@ -29,18 +30,14 @@ class Report
     /**
      * The trial results.
      *
-     * @var array
+     * @var Result[]
      */
     protected $trials = [];
 
     /**
      * Create a new result instance.
-     *
-     * @param string            $name
-     * @param \Scientist\Result $control
-     * @param array             $trials
      */
-    public function __construct($name, Result $control, array $trials = [])
+    public function __construct(string $name, Result $control, array $trials = [])
     {
         $this->name    = $name;
         $this->control = $control;
@@ -49,32 +46,24 @@ public function __construct($name, Result $control, array $trials = [])
 
     /**
      * Get the experiment name.
-     *
-     * @return string
      */
-    public function getName()
+    public function getName(): string
     {
         return $this->name;
     }
 
     /**
      * Get the control result instance.
-     *
-     * @return \Scientist\Result
      */
-    public function getControl()
+    public function getControl(): Result
     {
         return $this->control;
     }
 
     /**
      * Get a trial result instance by name.
-     *
-     * @param string $name
-     *
-     * @return \Scientist\Result
      */
-    public function getTrial($name)
+    public function getTrial(string $name): Result
     {
         return $this->trials[$name];
     }
@@ -82,9 +71,9 @@ public function getTrial($name)
     /**
      * Get the trial result instances.
      *
-     * @return array
+     * @return Result[]
      */
-    public function getTrials()
+    public function getTrials(): array
     {
         return $this->trials;
     }
diff --git a/src/Result.php b/src/Result.php
index 6e78329..c961ee7 100644
--- a/src/Result.php
+++ b/src/Result.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace Scientist;
 
 use Exception;
@@ -58,7 +60,7 @@ class Result
     /**
      * Does the callback result value match the control.
      *
-     * @var boolean
+     * @var bool
      */
     protected $match = false;
 
@@ -67,6 +69,9 @@ class Result
      */
     protected $context;
 
+    /**
+     * @param ?mixed $context
+     */
     public function __construct($context = null)
     {
         $this->context = $context;
@@ -86,10 +91,8 @@ public function getValue()
      * Set the callback result value.
      *
      * @param mixed $value
-     *
-     * @return $this
      */
-    public function setValue($value)
+    public function setValue($value): self
     {
         $this->value = $value;
 
@@ -98,22 +101,16 @@ public function setValue($value)
 
     /**
      * Get the callback execution start time.
-     *
-     * @return float
      */
-    public function getStartTime()
+    public function getStartTime(): float
     {
         return $this->startTime;
     }
 
     /**
      * Set the callback execution start time.
-     *
-     * @param float $startTime
-     *
-     * @return $this
      */
-    public function setStartTime($startTime)
+    public function setStartTime(float $startTime): self
     {
         $this->startTime = $startTime;
 
@@ -122,22 +119,16 @@ public function setStartTime($startTime)
 
     /**
      * Get the callback execution end time.
-     *
-     * @return float
      */
-    public function getEndTime()
+    public function getEndTime(): float
     {
         return $this->endTime;
     }
 
     /**
      * Set the callback execution end time.
-     *
-     * @param float $endTime
-     *
-     * @return $this
      */
-    public function setEndTime($endTime)
+    public function setEndTime(float $endTime): self
     {
         $this->endTime = $endTime;
 
@@ -146,32 +137,24 @@ public function setEndTime($endTime)
 
     /**
      * Get the execution time of the callback.
-     *
-     * @return float
      */
-    public function getTime()
+    public function getTime(): float
     {
         return $this->endTime - $this->startTime;
     }
 
     /**
      * Get the callback execution starting memory usage.
-     *
-     * @return float
      */
-    public function getStartMemory()
+    public function getStartMemory(): float
     {
         return $this->startMemory;
     }
 
     /**
      * Set the callback execution starting memory usage.
-     *
-     * @param float $startMemory
-     *
-     * @return $this
      */
-    public function setStartMemory($startMemory)
+    public function setStartMemory(float $startMemory): self
     {
         $this->startMemory = $startMemory;
 
@@ -180,22 +163,16 @@ public function setStartMemory($startMemory)
 
     /**
      * Get the callback execution ending memory usage.
-     *
-     * @return float
      */
-    public function getEndMemory()
+    public function getEndMemory(): float
     {
         return $this->endMemory;
     }
 
     /**
      * Set the callback execution ending memory usage.
-     *
-     * @param float $endMemory
-     *
-     * @return $this
      */
-    public function setEndMemory($endMemory)
+    public function setEndMemory(float $endMemory): self
     {
         $this->endMemory = $endMemory;
 
@@ -204,38 +181,33 @@ public function setEndMemory($endMemory)
 
     /**
      * Get the memory spike amount of the callback.
-     *
-     * @return float
      */
-    public function getMemory()
+    public function getMemory(): float
     {
         return $this->endMemory - $this->startMemory;
     }
 
     /**
      * Get the exception thrown by the callback.
-     *
-     * @return Exception|null
      */
-    public function getException()
+    public function getException(): ?\Throwable
     {
         return $this->exception;
     }
 
     /**
      * Set the exception thrown by the callback.
-     *
-     * @param Exception|null $exception
-     *
-     * @return $this
      */
-    public function setException($exception)
+    public function setException(?\Throwable $exception): self
     {
         $this->exception = $exception;
 
         return $this;
     }
 
+    /**
+     * @return mixed
+     */
     public function getContext()
     {
         return $this->context;
@@ -243,22 +215,16 @@ public function getContext()
 
     /**
      * Determine whether the callback result matches the control.
-     *
-     * @return boolean
      */
-    public function isMatch()
+    public function isMatch(): bool
     {
         return $this->match;
     }
 
     /**
      * Set whether the callback result matches the control.
-     *
-     * @param boolean $match
-     *
-     * @return $this
      */
-    public function setMatch($match)
+    public function setMatch(bool $match): self
     {
         $this->match = $match;
 
diff --git a/src/Trial.php b/src/Trial.php
index c553687..685a96b 100644
--- a/src/Trial.php
+++ b/src/Trial.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace Scientist;
 
@@ -19,23 +20,29 @@ class Trial
      */
     protected $context;
 
-    public function __construct($name, callable $callback, $context)
+    /**
+     * @param mixed $context
+     */
+    public function __construct(string $name, callable $callback, $context)
     {
         $this->name = $name;
         $this->callback = $callback;
         $this->context = $context;
     }
 
-    public function getName()
+    public function getName(): string
     {
         return $this->name;
     }
 
-    public function getCallback()
+    public function getCallback(): callable
     {
         return $this->callback;
     }
 
+    /**
+     * @return mixed
+     */
     public function getContext()
     {
         return $this->context;
diff --git a/tests/Chances/StandardChanceTest.php b/tests/Chances/StandardChanceTest.php
index 9653134..35eb30a 100644
--- a/tests/Chances/StandardChanceTest.php
+++ b/tests/Chances/StandardChanceTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace Scientist\Chances;
 
 class StandardChanceTest extends \PHPUnit\Framework\TestCase
diff --git a/tests/ExperimentTest.php b/tests/ExperimentTest.php
index 6ff9692..0bf4ae7 100644
--- a/tests/ExperimentTest.php
+++ b/tests/ExperimentTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Experiment;
 use Scientist\Laboratory;
diff --git a/tests/InternTest.php b/tests/InternTest.php
index 1801fcb..1bfc004 100644
--- a/tests/InternTest.php
+++ b/tests/InternTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Intern;
 use Scientist\Report;
diff --git a/tests/Journals/JournalTest.php b/tests/Journals/JournalTest.php
index 63b4032..e68f359 100644
--- a/tests/Journals/JournalTest.php
+++ b/tests/Journals/JournalTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Report;
 use Scientist\Laboratory;
diff --git a/tests/LaboratoryTest.php b/tests/LaboratoryTest.php
index 00f5254..047cfda 100644
--- a/tests/LaboratoryTest.php
+++ b/tests/LaboratoryTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Report;
 use Scientist\Laboratory;
@@ -39,12 +40,12 @@ public function test_laboratory_can_fetch_report_for_experiment_with_no_journals
         $this->assertIsFloat($r->getTrial('trial')->getStartTime());
         $this->assertIsFloat($r->getTrial('trial')->getEndTime());
         $this->assertIsFloat($r->getTrial('trial')->getTime());
-        $this->assertIsInt($r->getControl()->getStartMemory());
-        $this->assertIsInt($r->getControl()->getEndMemory());
-        $this->assertIsInt($r->getControl()->getMemory());
-        $this->assertIsInt($r->getTrial('trial')->getStartMemory());
-        $this->assertIsInt($r->getTrial('trial')->getEndMemory());
-        $this->assertIsInt($r->getTrial('trial')->getMemory());
+        $this->assertIsFloat($r->getControl()->getStartMemory());
+        $this->assertIsFloat($r->getControl()->getEndMemory());
+        $this->assertIsFloat($r->getControl()->getMemory());
+        $this->assertIsFloat($r->getTrial('trial')->getStartMemory());
+        $this->assertIsFloat($r->getTrial('trial')->getEndMemory());
+        $this->assertIsFloat($r->getTrial('trial')->getMemory());
         $this->assertNull($r->getControl()->getException());
         $this->assertNull($r->getTrial('trial')->getException());
         $this->assertFalse($r->getTrial('trial')->isMatch());
diff --git a/tests/MachineTest.php b/tests/MachineTest.php
index 30841d6..f913860 100644
--- a/tests/MachineTest.php
+++ b/tests/MachineTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Result;
 use Scientist\Machine;
@@ -107,7 +108,7 @@ public function test_that_machine_can_determine_memory_usage_changes()
 
         $r = $m->execute();
 
-        $this->assertIsInt($r->getStartMemory());
-        $this->assertIsInt($r->getEndMemory());
+        $this->assertIsFloat($r->getStartMemory());
+        $this->assertIsFloat($r->getEndMemory());
     }
 }
diff --git a/tests/Matchers/ClosureMatcherTest.php b/tests/Matchers/ClosureMatcherTest.php
index 61641b2..ccb07ba 100644
--- a/tests/Matchers/ClosureMatcherTest.php
+++ b/tests/Matchers/ClosureMatcherTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Matchers\ClosureMatcher;
 
diff --git a/tests/Matchers/StandardMatcherTest.php b/tests/Matchers/StandardMatcherTest.php
index 0c1941b..72441d0 100644
--- a/tests/Matchers/StandardMatcherTest.php
+++ b/tests/Matchers/StandardMatcherTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Matchers\StandardMatcher;
 
diff --git a/tests/ReportTest.php b/tests/ReportTest.php
index 7db8950..4669397 100644
--- a/tests/ReportTest.php
+++ b/tests/ReportTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Result;
 use Scientist\Report;
diff --git a/tests/ResultTest.php b/tests/ResultTest.php
index 18bdea4..e279368 100644
--- a/tests/ResultTest.php
+++ b/tests/ResultTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 use Scientist\Result;
 
@@ -57,7 +58,7 @@ public function test_result_can_have_match_status()
     {
         $r = new Result;
         $r->setMatch(true);
-        $this->assertTrue(true, $r->isMatch());
+        $this->assertTrue($r->isMatch());
     }
 
     public function test_can_have_context()