diff --git a/examples/fail.yaml b/examples/fail.yaml
new file mode 100644
index 0000000..4e77499
--- /dev/null
+++ b/examples/fail.yaml
@@ -0,0 +1,7 @@
+---
+phases:
+- name: main
+  tasks:
+  - name: fail
+    command:
+      command: "false"
diff --git a/examples/main_test.go b/examples/main_test.go
index 40eabb8..5a1f4f6 100644
--- a/examples/main_test.go
+++ b/examples/main_test.go
@@ -15,25 +15,31 @@ func TestBuildflow(t *testing.T) {
 		{
 			title: "hello world",
 			file:  "hello_world.yaml",
-			exp: icmd.Expected{
-				ExitCode: 0,
-				Err:      "",
-			},
 		},
 		{
 			title: "run tasks in parallel",
 			file:  "parallel.yaml",
-			exp: icmd.Expected{
-				ExitCode: 0,
-				Err:      "",
-			},
 		},
 		{
 			title: "the task bar depends on the task foo",
 			file:  "task_dependency.yaml",
+		},
+		{
+			title: "task.when is true",
+			file:  "task_when_true.yaml",
+		},
+		{
+			title: "buildflow run fails as expected",
+			file:  "fail.yaml",
+			exp: icmd.Expected{
+				ExitCode: 1,
+			},
+		},
+		{
+			title: "if there are unknown fields in configuration file, buildflow run fails",
+			file:  "unknown_field.yaml",
 			exp: icmd.Expected{
-				ExitCode: 0,
-				Err:      "",
+				ExitCode: 1,
 			},
 		},
 	}
diff --git a/examples/task_when_true.yaml b/examples/task_when_true.yaml
new file mode 100644
index 0000000..a62bcb4
--- /dev/null
+++ b/examples/task_when_true.yaml
@@ -0,0 +1,8 @@
+---
+phases:
+- name: main
+  tasks:
+  - name: "when true"
+    command:
+      command: ":"
+    when: true
diff --git a/examples/unknown_field.yaml b/examples/unknown_field.yaml
new file mode 100644
index 0000000..acf7e42
--- /dev/null
+++ b/examples/unknown_field.yaml
@@ -0,0 +1,7 @@
+---
+phases:
+- name: main
+  tsks: # typo
+  - name: hello
+    command:
+      command: echo hello