diff --git a/include/query.h b/include/query.h
index f267fd7..9ce62f0 100644
--- a/include/query.h
+++ b/include/query.h
@@ -14,11 +14,11 @@ enum OPERATORS {
 
 
 struct join_params {
-    bool (*check)(int *in1, int *in2);
+    bool (*check)(const int *in1, const int *in2);
 };
 
 struct filter_params {
-    bool (*check)(int *in);
+    bool (*check)(const int *in);
 };
 
 struct window_params {
@@ -27,7 +27,7 @@ struct window_params {
 
 
 typedef union Parameters {
-    struct join_params join;
+    struct join_params   join;
     struct filter_params filter;
     struct window_params window;
 } parameter_t;
diff --git a/src/query.c b/src/query.c
index 8419583..34add34 100644
--- a/src/query.c
+++ b/src/query.c
@@ -4,22 +4,21 @@
 #include "query.h"
 
 #include <assert.h>
-#include <stdio.h>
 #include <stdlib.h>
 
 
-void join(int *in1, int *in2, int **out, parameter_t param)
+void join(const int *in1, const int *in2, int **out, const parameter_t param)
 {
     int *local_out = malloc(sizeof(int));
     *out = local_out;
-    printf("The join funftion\n");
+
     if (param.join.check(in1, in2)) {
-        printf("Join allowed\n");
+        *local_out = (*in1) + (*in2);
     }
 };
 
 
-void filter(int *in, int **out, parameter_t param)
+void filter(const int *in, int **out, const parameter_t param)
 {
     int *local_out = malloc(sizeof(int));
     *out = local_out;
@@ -30,12 +29,12 @@ void filter(int *in, int **out, parameter_t param)
 }
 
 
-void window(int *in, int **out, parameter_t param)
+void window(const int *in, int **out, const parameter_t param)
 {
     int *local_out = malloc(sizeof(int));
     *out = local_out;
-    printf("The window function, %p\n", in);
-    printf("The window size is: %i\n", param.window.window_size);
+
+    *local_out = (*in) * param.window.window_size;
 }
 
 
diff --git a/tests/queryTests.cpp b/tests/queryTests.cpp
index 38dd3c9..9d173d5 100644
--- a/tests/queryTests.cpp
+++ b/tests/queryTests.cpp
@@ -7,17 +7,18 @@ extern "C" {
     #include "query.h"
 }
 
-bool check_join(int *in1, int *in2)
+bool check_join(const int *in1, const int *in2)
 {
     return *in1 > *in2;
 }
 
-TEST(QueryTests, test_query_join_no_children) {
-    int *ptr;
+TEST(QueryTests, test_query_join_death_no_children)
+{
+    int *ptr = nullptr;
     operator_t join_op = {
         .type = JOIN,
-        .left = NULL,
-        .right = NULL,
+        .left = nullptr,
+        .right = nullptr,
         .params = {check_join}
     };
     query_t query_join = {.root = &join_op};
@@ -26,11 +27,12 @@ TEST(QueryTests, test_query_join_no_children) {
     ASSERT_DEATH(execute_query(&query_join, ptr, &ptr), "");
 }
 
-TEST(QueryTests, test_query_join_death_no_left_child) {
-    int *ptr;
+TEST(QueryTests, test_query_join_death_no_left_child)
+{
+    int *ptr = nullptr;
     operator_t join_op = {
         .type = JOIN,
-        .left = NULL,
+        .left = nullptr,
         .right = &join_op,
         .params = {check_join}
     };
@@ -40,12 +42,13 @@ TEST(QueryTests, test_query_join_death_no_left_child) {
     ASSERT_DEATH(execute_query(&query_join, ptr, &ptr), "");
 }
 
-TEST(QueryTests, test_query_join_death_no_right_child) {
-    int *ptr;
+TEST(QueryTests, test_query_join_death_no_right_child)
+{
+    int *ptr = nullptr;
     operator_t join_op = {
         .type = JOIN,
         .left = &join_op,
-        .right = NULL,
+        .right = nullptr,
         .params = {check_join}
     };
     query_t query_join = {.root = &join_op};
@@ -55,19 +58,20 @@ TEST(QueryTests, test_query_join_death_no_right_child) {
 }
 
 
-bool check_filter(int *in)
+bool check_filter(const int *in)
 {
     return *in < 2;
 }
 
-TEST(QueryTests, test_query_filter) {
+TEST(QueryTests, test_query_filter)
+{
     int input = 0;
     int *out;
 
     operator_t filter_op = {
         .type = FILTER,
-        .left = NULL,
-        .right = NULL,
+        .left = nullptr,
+        .right = nullptr,
         .params = {.filter = check_filter}
     };
 
@@ -76,5 +80,118 @@ TEST(QueryTests, test_query_filter) {
     execute_query(&query_filter, &input, &out);
     ASSERT_EQ(*out, 1);
 
+    free(out);
+}
+
+
+TEST(QueryTests, test_query_filter2)
+{
+    int input = 0;
+    int *out;
+
+    operator_t filter_op = {
+        .type = FILTER,
+        .left = nullptr,
+        .right = nullptr,
+        .params = {.filter = check_filter}
+    };
+
+    operator_t filter_op2 = {
+        .type = FILTER,
+        .left = &filter_op,
+        .right = nullptr,
+        .params = {.filter = check_filter}
+    };
+
+    query_t query_filter = {.root = &filter_op2};
+
+    execute_query(&query_filter, &input, &out);
+    ASSERT_EQ(*out, 2);
+
+    free(out);
+}
+
+
+TEST(QueryTests, test_query_window)
+{
+    int input = 1;
+    int *out;
+
+    operator_t window_op = {
+        .type = WINDOW,
+        .left = nullptr,
+        .right = nullptr,
+        .params = {.window = 10}
+    };
+
+    query_t query_window = {.root = &window_op};
+
+    execute_query(&query_window, &input, &out);
+    ASSERT_EQ(*out, 10);
+
+    free(out);
+}
+
+
+TEST(QueryTests, test_query_window2)
+{
+    int input = 1;
+    int *out;
+
+    operator_t window_op = {
+        .type = WINDOW,
+        .left = nullptr,
+        .right = nullptr,
+        .params = {.window = 10}
+    };
+
+    operator_t window_op2 = {
+        .type = WINDOW,
+        .left = &window_op,
+        .right = nullptr,
+        .params = {.window = 5}
+    };
+
+    query_t query_window = {.root = &window_op2};
+
+    execute_query(&query_window, &input, &out);
+    ASSERT_EQ(*out, 50);
+
+    free(out);
+}
+
+
+TEST(QueryTests, test_query_join)
+{
+    int input = 1;
+    int *out;
+
+    operator_t window_op = {
+        .type = WINDOW,
+        .left = nullptr,
+        .right = nullptr,
+        .params = {.window = 10}
+    };
+
+    operator_t filter_op = {
+        .type = FILTER,
+        .left = nullptr,
+        .right = nullptr,
+        .params = {.filter = check_filter}
+    };
+
+    operator_t join_op = {
+        .type = JOIN,
+        .left = &window_op,
+        .right = &filter_op,
+        .params = {.join = check_join}
+    };
+
+    query_t query = {.root = &join_op};
+
+    execute_query(&query, &input, &out);
+
+    ASSERT_EQ(*out, 12);
+
     free(out);
 }
\ No newline at end of file