diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..8a21474
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,91 @@
+name: CI
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+
+      - name: version info
+        run:  rustc --version; cargo --version;
+
+      - name: Run all tests
+        run: cargo test
+
+  fmt:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+
+      - uses: actions-rs/cargo@v1
+        with:
+          command: fmt
+          args: --all -- --check
+
+  clippy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+
+      - uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+          args: -- -D warnings
+
+
+  sass-spec:
+    continue-on-error: true
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+
+      - name: version info
+        run:  rustc --version; cargo --version;
+
+      - name: Build binary
+        run: cargo b --release
+
+      - name: Get sass-spec
+        run: git submodule init && git submodule update
+
+      - name: Install whatever Ruby needs
+        run: |
+          sudo apt-get install libncurses5-dev libncursesw5-dev
+          sudo gem install bundler
+          cd sass-spec && bundler install
+
+      - name: Run Sass spec
+        run: ./sass-spec/sass-spec.rb -c './target/release/grass'
diff --git a/.gitignore b/.gitignore
index c08fa70..2089ed5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,5 @@
 Cargo.lock
 coverage
 pkg
+.idea/
+!input.scss
\ No newline at end of file
diff --git a/input.scss b/input.scss
new file mode 100644
index 0000000..80afe79
--- /dev/null
+++ b/input.scss
@@ -0,0 +1,3 @@
+body {
+  background: red;
+}
\ No newline at end of file
diff --git a/src/args.rs b/src/args.rs
index 0ae0583..7cf5e38 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -5,7 +5,6 @@ use codemap::{Span, Spanned};
 
 use peekmore::PeekMoreIterator;
 
-use crate::Cow;
 use crate::common::Identifier;
 use crate::error::SassResult;
 use crate::scope::Scope;
@@ -15,6 +14,7 @@ use crate::utils::{
     read_until_closing_paren, read_until_closing_quote, read_until_closing_square_brace,
 };
 use crate::value::Value;
+use crate::Cow;
 use crate::Token;
 
 #[derive(Debug, Clone, Eq, PartialEq)]
diff --git a/src/atrule/media.rs b/src/atrule/media.rs
index 70dd2d1..99e3f10 100644
--- a/src/atrule/media.rs
+++ b/src/atrule/media.rs
@@ -64,9 +64,7 @@ impl Media {
             }
         }
 
-        if super_selector.is_empty() {
-            body.append(&mut rules);
-        } else {
+        if !super_selector.is_empty() {
             body = vec![Spanned {
                 node: Stmt::RuleSet(RuleSet {
                     selector: super_selector.clone(),
@@ -75,8 +73,8 @@ impl Media {
                 }),
                 span: kind_span,
             }];
-            body.append(&mut rules);
         }
+        body.append(&mut rules);
 
         Ok(Media {
             super_selector: Selector::new(),
diff --git a/src/utils/strings.rs b/src/utils/strings.rs
index 4573941..9eda2e5 100644
--- a/src/utils/strings.rs
+++ b/src/utils/strings.rs
@@ -1,5 +1,5 @@
-use std::iter::Iterator;
 use std::borrow::Borrow;
+use std::iter::Iterator;
 
 use codemap::{Span, Spanned};
 
diff --git a/src/value/ops.rs b/src/value/ops.rs
index 5d63d97..0c0e0c8 100644
--- a/src/value/ops.rs
+++ b/src/value/ops.rs
@@ -324,7 +324,9 @@ impl Value {
                     format!("{}{}", self.to_css_string(span)?, s),
                     QuoteKind::Quoted,
                 ),
-                Self::Null => Value::String(self.to_css_string(span)?.into_owned(), QuoteKind::None),
+                Self::Null => {
+                    Value::String(self.to_css_string(span)?.into_owned(), QuoteKind::None)
+                }
                 _ => Value::String(
                     format!(
                         "{}{}",
diff --git a/src/value/parse.rs b/src/value/parse.rs
index 7c49e53..5e818fe 100644
--- a/src/value/parse.rs
+++ b/src/value/parse.rs
@@ -431,6 +431,12 @@ fn single_value<I: Iterator<Item = Token>>(
     })
 }
 
+fn parse_i64(s: String) -> i64 {
+    s.as_bytes()
+        .iter()
+        .fold(0, |total, this| total * 10 + i64::from(this - b'0'))
+}
+
 impl Value {
     pub fn from_tokens<I: Iterator<Item = Token>>(
         toks: &mut PeekMoreIterator<I>,
@@ -735,7 +741,7 @@ impl Value {
 
                 let n = if val.dec_len == 0 {
                     if val.num.len() <= 18 && val.times_ten.is_empty() {
-                        let n = Rational64::new_raw(val.num.parse::<i64>().unwrap(), 1);
+                        let n = Rational64::new_raw(parse_i64(val.num), 1);
                         return Some(Ok(IntermediateValue::Value(Value::Dimension(
                             Number::new_machine(n),
                             unit,
@@ -745,8 +751,7 @@ impl Value {
                     BigRational::new_raw(val.num.parse::<BigInt>().unwrap(), BigInt::one())
                 } else {
                     if val.num.len() <= 18 && val.times_ten.is_empty() {
-                        let n =
-                            Rational64::new(val.num.parse::<i64>().unwrap(), pow(10, val.dec_len));
+                        let n = Rational64::new(parse_i64(val.num), pow(10, val.dec_len));
                         return Some(Ok(IntermediateValue::Value(Value::Dimension(
                             Number::new_machine(n),
                             unit,