diff --git a/app/models/mood.rb b/app/models/mood.rb
index c065440..89d5501 100644
--- a/app/models/mood.rb
+++ b/app/models/mood.rb
@@ -1,4 +1,19 @@
 class Mood < ApplicationRecord
   belongs_to :user
   belongs_to :mode
+
+  validates :recorded_at, presence: true
+  validate :unique_per_day_and_user
+
+  private
+
+  def unique_per_day_and_user
+    return unless recorded_at && user
+
+    existing = user.moods.where.not(id: id).any? do |mood|
+      mood.recorded_at.to_date == recorded_at.to_date
+    end
+
+    errors.add(:recorded_at, :taken) if existing
+  end
 end
diff --git a/spec/factories/moods.rb b/spec/factories/moods.rb
index e75d860..127c759 100644
--- a/spec/factories/moods.rb
+++ b/spec/factories/moods.rb
@@ -1,7 +1,7 @@
 FactoryBot.define do
   factory :mood do
-    mode { "croisiere" }
-    recorded_at { DateTime.now }
+    recorded_at { DateTime.parse("2026-01-15 10:00:00") }
     association :user
+    association :mode
   end
 end
diff --git a/spec/models/mood_spec.rb b/spec/models/mood_spec.rb
index 3dc71c8..54ef1b4 100644
--- a/spec/models/mood_spec.rb
+++ b/spec/models/mood_spec.rb
@@ -1,7 +1,46 @@
 require 'rails_helper'
 
-describe Mood, type: :model do
-  it 'works' do
-    expect(true)
+describe Mood do
+  let(:user) { create(:user) }
+  let(:mode) { create(:mode, user: user) }
+
+  subject { build(:mood, user: user, mode: mode, recorded_at: DateTime.parse("2026-01-15 10:00:00")) }
+
+  it { is_expected.to be_valid }
+
+  describe "validations" do
+    it "is invalid without a user" do
+      subject.user = nil
+      expect(subject).not_to be_valid
+    end
+
+    it "is invalid without a mode" do
+      subject.mode = nil
+      expect(subject).not_to be_valid
+    end
+
+    it "is invalid without a recorded_at" do
+      subject.recorded_at = nil
+      expect(subject).not_to be_valid
+    end
+  end
+
+  describe "uniqueness per day and user" do
+    it "is invalid if a mood already exists for the same day and user" do
+      create(:mood, user: user, mode: mode, recorded_at: DateTime.parse("2026-01-15 18:00:00"))
+      expect(subject).not_to be_valid
+    end
+
+    it "is valid if the same day exists but for a different user" do
+      other_user = create(:user)
+      other_mode = create(:mode, user: other_user)
+      create(:mood, user: other_user, mode: other_mode, recorded_at: DateTime.parse("2026-01-15 10:00:00"))
+      expect(subject).to be_valid
+    end
+
+    it "is valid if the same user has a mood on a different day" do
+      create(:mood, user: user, mode: mode, recorded_at: DateTime.parse("2026-01-14 10:00:00"))
+      expect(subject).to be_valid
+    end
   end
 end