diff --git a/.gitignore b/.gitignore
index dcc0cc6..ac0f37b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
-html/
-build/dist
\ No newline at end of file
+/html/
+/build/dist
+/coverage.out
diff --git a/build/ci/.drone.yml b/build/ci/.drone.yml
index 41d3713..db5e62e 100644
--- a/build/ci/.drone.yml
+++ b/build/ci/.drone.yml
@@ -6,7 +6,7 @@ workspace:
   path: src/gitbase.de/apairon/mark2web
 
 steps:
-  - name: build for linux
+  - name: test
     image: golang:latest
     environment:
       CGO_ENABLED: 0
@@ -15,6 +15,17 @@ steps:
     commands:
       - git submodule update --init --recursive
       - git fetch --tags
+      - go test -v -coverprofile coverage.out ./pkg/*
+    when:
+      event: [ push, tag ]
+
+  - name: build for linux
+    image: golang:latest
+    environment:
+      CGO_ENABLED: 0
+      GOOS: linux
+      GOARCH: amd64
+    commands:
       - scripts/build.sh
     when:
       event: [ push, tag ]
diff --git a/pkg/filter/dump_test.go b/pkg/filter/dump_test.go
new file mode 100644
index 0000000..4925345
--- /dev/null
+++ b/pkg/filter/dump_test.go
@@ -0,0 +1,24 @@
+package filter
+
+import (
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+
+	"github.com/flosch/pongo2"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestDumpFilter(t *testing.T) {
+	Convey("set context", t, func() {
+		ctx := pongo2.Context{
+			"testvar": "test",
+		}
+		Convey("parse template", func() {
+			output, err := pongo2.RenderTemplateString("{{ testvar|safe|dump }}", ctx)
+			So(err, ShouldBeNil)
+			So(output, ShouldEqual, spew.Sdump("test"))
+		})
+	})
+}
diff --git a/pkg/filter/json_test.go b/pkg/filter/json_test.go
new file mode 100644
index 0000000..2d1bcbe
--- /dev/null
+++ b/pkg/filter/json_test.go
@@ -0,0 +1,50 @@
+package filter
+
+import (
+	"math"
+	"testing"
+
+	"github.com/flosch/pongo2"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestJSONFilter(t *testing.T) {
+	Convey("set context", t, func() {
+		ctx := pongo2.Context{
+			"teststr": "test",
+			"testmap": map[string]interface{}{
+				"float": 1.23,
+				"int":   5,
+				"str":   "test",
+			},
+			"testerr": math.Inf(1),
+		}
+		Convey("parse template", func() {
+			output, err := pongo2.RenderTemplateString("{{ teststr|safe|json }}", ctx)
+			So(err, ShouldBeNil)
+			So(output, ShouldEqual, `"test"`)
+
+			output, err = pongo2.RenderTemplateString("{{ testmap|safe|json }}", ctx)
+			So(err, ShouldBeNil)
+			So(output, ShouldEqual, `{"float":1.23,"int":5,"str":"test"}`)
+
+			output, err = pongo2.RenderTemplateString(`{{ testmap|safe|json:"pretty" }}`, ctx)
+			So(err, ShouldBeNil)
+			So(output, ShouldEqual, `{
+    "float": 1.23,
+    "int": 5,
+    "str": "test"
+}`)
+
+			output, err = pongo2.RenderTemplateString("{{ testnil|safe|json }}", ctx)
+			So(err, ShouldBeNil)
+			So(output, ShouldEqual, `null`)
+
+			output, err = pongo2.RenderTemplateString("{{ testerr|safe|json }}", ctx)
+			So(err, ShouldNotBeNil)
+			So(output, ShouldEqual, ``)
+
+		})
+	})
+}