diff --git a/25-testing/01-testify/.README.md b/25-testing/01-testify/.README.md
new file mode 100644
index 0000000..b4ca601
--- /dev/null
+++ b/25-testing/01-testify/.README.md
@@ -0,0 +1,95 @@
+# Testing
+
+In this task, you need to test the function `{{ index . "name" }}` in Go using **`testify/assert`**.
+
+## Function Description
+
+The implementation is available in [exercise_test.go](exercise_test.go), if needed.
+Below we show some examples of the expected behaviors.
+
+{{- if eq (index . "name") "strstr" }}
+
+### `strstr(str string, substr string) int`
+
+- Returns the **index of the first occurrence** of `substr` in `str`.
+- Returns `0` if `substr` is empty.
+- Returns `-1` if `substr` is not found.
+
+**Example:**
+
+```go
+strstr("hello world", "lo")  // 3
+
+strstr("hello", "Go")        // -1
+
+strstr("abc", "")            // 0
+```
+{{- end }}
+{{- if eq (index . "name") "strncat" }}
+
+### `strncat(dest *string, src string, n int)`
+
+- Appends at most `n` characters from `src` to `dest`.
+- Modifies `dest` in place
+
+**Example:**
+
+```go
+dest := "Hello"
+strncat(&dest, "World", 3) // dest == "HelloWor"
+
+dest := "Hi"
+strncat(&dest, "All", 10)  // dest == "HiAll"
+
+dest := ""
+strncat(&dest, "Go", 1)    // dest == "G"
+```
+{{- end }}
+{{- if eq (index . "name") "strncpy" }}
+
+### `strncpy(dest *string, src string, n int)`
+
+- Copies at most `n` characters from `src` to `dest`.
+- Modifies `dest` in place
+
+**Example:**
+
+```go
+dest := "Hello"
+strncpy(&dest, "Go", 2)    // dest == "Go"
+
+dest := ""
+strncpy(&dest, "World", 3) // dest == "Wor"
+
+dest := "Hi"
+strncpy(&dest, "", 1)      // dest == ""
+```
+{{- end }}
+
+## Requirements
+1. Use only assert statements from the [testify/assert](https://pkg.go.dev/github.com/stretchr/testify/assert) package.
+2. Do not modify the provided function signature.
+3. Write exactly three test functions for the function `{{ index . "name" }}`.
+
+## Needed test functions:
+
+{{- if eq (index . "name") "strstr" }}
+
+- `StrStrMatch(t *testing.T)` — test when the substring exists
+- `StrStrNoMatch(t *testing.T)` — test when the substring does not exist
+- `StrStrEmptySubString(t *testing.T)` — test when the substring is empty
+{{- end }}
+{{- if eq (index . "name") "strncat" }}
+
+- `StrNCatInbounds(t *testing.T)` — append a part of the source within index bounds
+- `StrNCatOutOfBounds(t *testing.T)` — append more than the source length
+- `StrNCatEmptySource(t *testing.T)` — append from an empty source
+{{- end }}
+{{- if eq (index . "name") "strncpy" }}
+
+- `StrNCpyINbounds(t *testing.T)` — copy part of the source within index bounds
+- `StrNCpyEmptyDestination(t *testing.T)` — copy into an empty destination
+- `StrNCpyEmptySource(t *testing.T)` — copy from an empty source
+{{- end }}
+
+Insert the code into the file `exercise.go` at the placeholder `// INSERT YOUR CODE HERE`.
diff --git a/25-testing/01-testify/.exercise_test.go b/25-testing/01-testify/.exercise_test.go
new file mode 100644
index 0000000..271d328
--- /dev/null
+++ b/25-testing/01-testify/.exercise_test.go
@@ -0,0 +1,115 @@
+package testimony
+
+import (
+	"os"
+	"regexp"
+	"testing"
+)
+
+const requiredAsserts = 3
+
+func TestStudentUsesAssertions(t *testing.T) {
+	src, err := os.ReadFile("exercise.go")
+	if err != nil {
+		t.Fatalf("cannot read exercise.go: %v", err)
+	}
+
+	source := string(src)
+
+	re := regexp.MustCompile(`assert\.\w+\s*\(`)
+	if !re.MatchString(source) {
+		t.Fatalf("no assert.* call found in exercise.go")
+	}
+}
+
+func TestStudentHasEnoughAsserts(t *testing.T) {
+	src, err := os.ReadFile("exercise.go")
+	if err != nil {
+		t.Fatalf("cannot read exercise.go: %v", err)
+	}
+
+	source := string(src)
+
+	re := regexp.MustCompile(`assert\.\w+\s*\(`)
+	matches := re.FindAllString(source, -1)
+
+	if len(matches) < requiredAsserts {
+		t.Fatalf("not enough assert calls: found %d, required %d", len(matches), requiredAsserts)
+	}
+}
+
+func TestNoTrivialAssertions(t *testing.T) {
+	src, err := os.ReadFile("exercise.go")
+	if err != nil {
+		t.Fatalf("cannot read exercise.go: %v", err)
+	}
+
+	source := string(src)
+
+	patterns := []string{
+		`assert\.False\s*\(\s*t\s*,\s*false\s*[,)]`,
+		`assert\.True\s*\(\s*t\s*,\s*true\s*[,)]`,
+		`assert\.Equal\s*\(\s*t\s*,\s*true\s*,\s*true\s*[,)]`,
+		`assert\.Equal\s*\(\s*t\s*,\s*false\s*,\s*false\s*[,)]`,
+	}
+
+	for _, p := range patterns {
+		re := regexp.MustCompile(p)
+		if re.MatchString(source) {
+			t.Fatalf("trivial assertion detected")
+		}
+	}
+}
+
+{{- if eq (index . "name") "strstr"}}
+
+func strstr(str string, substr string) int {
+	if substr == "" {
+		return 0
+	}
+
+	for i := 0; i <= len(str)-len(substr); i++ {
+		if str[i:i+len(substr)] == substr {
+			return i
+		}
+	}
+
+	return -1
+}
+{{- end}}
+{{- if eq (index . "name") "strncat"}}
+
+func strncat(dest *string, src string, n int) {
+	if n > len(src) {
+		n = len(src)
+	}
+	*dest += src[:n]
+}
+{{- end}}
+{{- if eq (index . "name") "strncpy"}}
+
+func strncpy(dest *string, src string, n int) {
+	if n > len(src) {
+		n = len(src)
+	}
+	*dest = src[:n]
+}
+{{- end}}
+
+func TestRunStudentTests(t *testing.T) {
+{{- if eq (index . "name") "strstr"}}
+	t.Run("StrStrMatch", StrStrMatch)
+	t.Run("StrStrNoMatch", StrStrNoMatch)
+	t.Run("StrStrEmptySubString", StrStrEmptySubString)
+{{- end}}
+{{- if eq (index . "name") "strncat"}}
+	t.Run("StrNCatInbounds", StrNCatInbounds)
+	t.Run("StrNCatOutOfBounds", StrNCatOutOfBounds)
+	t.Run("StrNCatEmptySource", StrNCatEmptySource)
+{{- end}}
+{{- if eq (index . "name") "strncpy"}}
+	t.Run("StrNCpyINbounds", StrNCpyINbounds)
+	t.Run("StrNCpyEmptyDestination", StrNCpyEmptyDestination)
+	t.Run("StrNCpyEmptySource", StrNCpyEmptySource)
+{{- end}}
+}
diff --git a/25-testing/01-testify/exercise.go b/25-testing/01-testify/exercise.go
new file mode 100644
index 0000000..ba32903
--- /dev/null
+++ b/25-testing/01-testify/exercise.go
@@ -0,0 +1,13 @@
+package testimony
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// DO NOT REMOVE THIS COMMENT
+//go:generate go run ../../exercises-cli.go -student-id=$STUDENT_ID generate
+
+
+// INSERT YOUR CODE HERE
diff --git a/25-testing/01-testify/exercise.yaml b/25-testing/01-testify/exercise.yaml
new file mode 100644
index 0000000..39bf2b0
--- /dev/null
+++ b/25-testing/01-testify/exercise.yaml
@@ -0,0 +1,5 @@
+name: testimony
+input:
+- name: strstr
+- name: strncat
+- name: strncpy
\ No newline at end of file
diff --git a/Makefile b/Makefile
index a11c9d1..6b79566 100644
--- a/Makefile
+++ b/Makefile
@@ -14,7 +14,8 @@ EXERCISE_DIRS=\
 	21-channels \
 	22-context \
 	23-misc \
-	24-generics
+	24-generics \
+	25-testing
 
 # LAB subdirs
 LAB_DIRS=\