diff --git a/test/c_not_python.query b/test/c_not_python.query
new file mode 100644
index 0000000..f1c52fc
--- /dev/null
+++ b/test/c_not_python.query
@@ -0,0 +1 @@
+πname (σ skill=='C' (people ⋈ skills)) - π name (σ skill=='Python' (people ⋈ skills))
diff --git a/test/c_not_python.result b/test/c_not_python.result
new file mode 100644
index 0000000..1899391
--- /dev/null
+++ b/test/c_not_python.result
@@ -0,0 +1,4 @@
+name
+eve
+john
+duncan
diff --git a/test/java_and_perl.query b/test/java_and_perl.query
new file mode 100644
index 0000000..7cdb47d
--- /dev/null
+++ b/test/java_and_perl.query
@@ -0,0 +1,2 @@
+πname (σ skill=='Perl' (people ⋈ skills)) ∪ π name (σ skill=='Java' (people ⋈ skills))
+
diff --git a/test/java_and_perl.result b/test/java_and_perl.result
new file mode 100644
index 0000000..02755db
--- /dev/null
+++ b/test/java_and_perl.result
@@ -0,0 +1,3 @@
+name
+duncan
+eve
diff --git a/test/python_and_c.query b/test/python_and_c.query
new file mode 100644
index 0000000..be883c1
--- /dev/null
+++ b/test/python_and_c.query
@@ -0,0 +1 @@
+πname (σ skill=='C' (people ⋈ skills)) ∩ π name (σ skill=='Python' (people ⋈ skills))
diff --git a/test/python_and_c.result b/test/python_and_c.result
new file mode 100644
index 0000000..6eb3d0c
--- /dev/null
+++ b/test/python_and_c.result
@@ -0,0 +1,3 @@
+name
+jack
+alia